diff --git a/package.json b/package.json
index a404fcf..1a0e5a8 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@agentlab/sparql-jsld-client",
-  "version": "5.0.0-rc.18",
+  "version": "5.0.0-rc.19",
   "description": "SPARQL JSON Schema Linked Data Client",
   "license": "GPL-3.0",
   "author": "Alexey Ivanov <amivanoff@gmail.com>",
diff --git a/src/models/MstColl.ts b/src/models/MstColl.ts
index 4bb6345..b099caf 100644
--- a/src/models/MstColl.ts
+++ b/src/models/MstColl.ts
@@ -188,7 +188,6 @@ export const MstColl = types
         //console.log('MstColl afterAttach, @id=', self['@id']);
         // first-time load
         if (self.lazy === false) {
-          self.isLoading = true;
           setImmediate(() => {
             //@ts-ignore
             self.loadColl();
@@ -201,7 +200,6 @@ export const MstColl = types
           },
           (newVal: any, oldVal: any) => {
             //console.log('MstColl.collConstr changed, reload data', { newVal, oldVal });
-            self.isLoading = true;
             setImmediate(() => {
               //@ts-ignore
               self.loadColl();
diff --git a/src/models/MstRepository.ts b/src/models/MstRepository.ts
index 817fe07..e5e9b22 100644
--- a/src/models/MstRepository.ts
+++ b/src/models/MstRepository.ts
@@ -275,17 +275,17 @@ export const MstRepository = types
        * @param by
        */
       editConn(connections: any[], data: any) {
-        //console.log('editConn START with data=', data);
+        //console.log('editConn START with data=', { connections, data });
         connections.forEach((conn: any) => {
           const toId = conn.toObj;
-          let value = conn.fromProp === undefined || data === undefined ? data : data[conn.fromProp];
+          let value = conn.fromProp === undefined || data === undefined || data === null ? data : data[conn.fromProp];
           //console.log('editConn conn with id=', toId);
           const node: any = values(self.colls).find((coll: any) => {
             //console.log('editConn coll=', getSnapshot(coll));
             //console.log('editConn collConstr=', getSnapshot(coll.collConstr));
             //console.log('editConn collConstr @id=', coll.collConstr['@id']);
             if (coll.collConstr['@id'] === toId) {
-              //console.log('editConn found coll.collConstr');
+              console.log('editConn found coll.collConstr, ignore it');
               return true;
             }
             return values(coll.collConstr.entConstrs).find((entConstr: any) => {
@@ -312,13 +312,13 @@ export const MstRepository = types
                     ...entConstrJs,
                   };
                   if (value !== undefined) {
-                    //console.log('editConn set key=', conn.toProp);
-                    entConstrJs[conn.toProp] = value;
+                    console.log('editConn set key=', conn.toProp);
+                    //entConstrJs[conn.toProp] = value;
                   } else {
                     //console.log('editConn delete key=', conn.toProp);
                     delete entConstrJs[conn.toProp];
                   }
-                  console.log('editConn set new entConstr=', entConstrJs);
+                  console.log('editConn set new entConstr by conn', { entConstrJs, conn });
                   applySnapshot(entConstr, entConstrJs);
                   //console.log('editConn applied entConstr=', entConstrJs);
                 }
@@ -357,7 +357,7 @@ export const MstRepository = types
                   //console.log('editConn delete key=', conn.toProp);
                   delete condition[conn.toProp];
                 }
-                console.log('editConn set new condition=', condition);
+                console.log('editConn set new condition by conn', { condition, conn });
                 applySnapshot(node, condition);
                 //console.log('editConn applied condition=', condition);
                 return true;
@@ -376,7 +376,7 @@ export const MstRepository = types
           //  applySnapshot(node, condition);
           //  console.log('editConn applied condition=', condition);
           //}
-          console.log('editConn END');
+          //console.log('editConn END');
         });
       },
 
diff --git a/src/models/MstSchemas.ts b/src/models/MstSchemas.ts
index 25b78f2..75142c9 100644
--- a/src/models/MstSchemas.ts
+++ b/src/models/MstSchemas.ts
@@ -220,8 +220,16 @@ export const MstSchemas = types
         } else {
           // TODO: this is ugly, but workaround the idea that views should be side effect free.
           // We need a more elegant solution.
-          //@ts-ignore
-          setImmediate(() => self.loadSchemaByClassIri(iri));
+          setImmediate(() => {
+            if (iri && !self.class2schema.has(iri)) {
+              try {
+                //@ts-ignore
+                self.loadSchemaByClassIri(iri);
+              } catch (err) {
+                console.log(err);
+              }
+            }
+          });
           return null;
         }
       },
@@ -233,21 +241,23 @@ export const MstSchemas = types
       getOrLoadSchemaByIri(iri: string | undefined) {
         if (!iri || iri.length === 0) return null;
         iri = abbreviateIri(iri, repository.ns.currentJs);
-        if (!self.json.has(iri)) {
-          // TODO: this is ugly, but workaround the idea that views should be side effect free.
-          // We need a more elegant solution.
-          setImmediate(async () => {
+        if (self.json.has(iri)) {
+          //console.log('getOrLoadSchemaByIri: return schema', iri);
+          return self.json.get(iri);
+        }
+        // TODO: this is ugly, but workaround the idea that views should be side effect free.
+        // We need a more elegant solution.
+        setImmediate(async () => {
+          if (iri && !self.json.has(iri)) {
             try {
               //@ts-ignore
               await self.loadSchemaByIri(iri);
             } catch (err) {
               console.log(err);
             }
-          });
-          return null;
-        } else {
-          return self.json.get(iri);
-        }
+          }
+        });
+        return null;
       },
     };
   })
@@ -292,6 +302,7 @@ export const MstSchemas = types
         for (let i = 0; i < schemaAllOf.length; i++) {
           const iri = schemaAllOf[i].$ref;
           if (!self.json.has(iri)) {
+            //console.log('getDirectSuperSchemas: load schema', iri);
             //@ts-ignore
             yield self.loadSchemaByIri(iri);
           }
@@ -324,6 +335,9 @@ export const MstSchemas = types
       return schema;
     };
 
+    const loadingByClass: any = {};
+    const loadingByIri: any = {};
+
     return {
       addSchema(schema: JSONSchema6forRdf): void {
         const iri: string = abbreviateIri(schema['@id'], repository.ns.currentJs);
@@ -346,8 +360,26 @@ export const MstSchemas = types
       loadSchemaByClassIri: flow(function* loadSchemaByClassIri(iri: string | undefined) {
         //console.log('loadSchemaByClassIri', iri);
         if (!iri || iri.length === 0) return;
-        const schemaObs = yield loadSchemaInternal({ targetClass: iri });
-        //console.log('END loadSchemaByClassIri', iri);
+        // check loaded repo
+        let schemaObs: any = self.class2schema.get(iri);
+        if (schemaObs !== undefined) {
+          schemaObs = self.json.get(schemaObs);
+          if (schemaObs !== undefined) return schemaObs;
+        }
+        // check loading process
+        let loadSchemaGen = loadingByClass[iri];
+        if (loadSchemaGen) {
+          //console.log('WAIT START loadSchemaByClassIri', iri);
+          schemaObs = yield loadSchemaGen;
+          //console.log('WAIT END loadSchemaByClassIri', iri);
+        } else {
+          //console.log('LOAD START loadSchemaByClassIri', iri);
+          loadSchemaGen = loadSchemaInternal({ targetClass: iri });
+          loadingByClass[iri] = loadSchemaGen;
+          schemaObs = yield loadSchemaGen;
+          delete loadingByClass[iri];
+          //console.log('LOAD END loadSchemaByClassIri', iri);
+        }
         return schemaObs;
       }),
 
@@ -359,8 +391,23 @@ export const MstSchemas = types
       loadSchemaByIri: flow(function* loadSchemaByIri(iri: string | undefined) {
         //console.log('loadSchemaByIri', iri);
         if (!iri || iri.length === 0) return;
-        const schemaObs = yield loadSchemaInternal({ '@_id': iri });
-        //console.log('END loadSchemaByIri', iri);
+        // check loaded repo
+        let schemaObs: any = self.json.get(iri);
+        if (schemaObs !== undefined) return schemaObs;
+        // check loading process
+        let loadSchemaGen = loadingByIri[iri];
+        if (loadSchemaGen) {
+          //console.log('WAIT START loadSchemaByIri', iri);
+          schemaObs = yield loadSchemaGen;
+          //console.log('WAIT END loadSchemaByIri', iri);
+        } else {
+          //console.log('LOAD START loadSchemaByIri', iri);
+          loadSchemaGen = loadSchemaInternal({ '@_id': iri });
+          loadingByIri[iri] = loadSchemaGen;
+          schemaObs = yield loadSchemaGen;
+          delete loadingByIri[iri];
+          //console.log('LOAD END loadSchemaByIri', iri);
+        }
         return schemaObs;
       }),
     };