diff --git a/packages/ketcher-core/src/application/editor/Editor.ts b/packages/ketcher-core/src/application/editor/Editor.ts
index 1f3d3418b4..af9b542269 100644
--- a/packages/ketcher-core/src/application/editor/Editor.ts
+++ b/packages/ketcher-core/src/application/editor/Editor.ts
@@ -82,8 +82,7 @@ export class CoreEditor {
   // todo we need to create abstraction layer for modes in future similar to the tools layer
   private onSelectMode(isSnakeMode: boolean) {
     PolymerBondRenderer.setSnakeMode(isSnakeMode);
-    let modelChanges;
-    modelChanges = this.drawingEntitiesManager.reArrangeChain(
+    const modelChanges = this.drawingEntitiesManager.reArrangeChain(
       this.canvas.width.baseVal.value,
       isSnakeMode,
     );
diff --git a/packages/ketcher-core/src/domain/entities/DrawingEntitiesManager.ts b/packages/ketcher-core/src/domain/entities/DrawingEntitiesManager.ts
index 5e26896f21..9e5d8c420f 100644
--- a/packages/ketcher-core/src/domain/entities/DrawingEntitiesManager.ts
+++ b/packages/ketcher-core/src/domain/entities/DrawingEntitiesManager.ts
@@ -509,7 +509,7 @@ export class DrawingEntitiesManager {
         chain[i - 1].position,
         editorSettings,
       );
-      let isMonomerFitCanvas =
+      const isMonomerFitCanvas =
         prevPosition.x +
           DISTANCE_BETWEEN_MONOMERS +
           initCoords.x +
@@ -556,14 +556,15 @@ export class DrawingEntitiesManager {
   private findChainByMonomer(monomer: BaseMonomer) {
     let firstMonomer = monomer;
     while (this.getPrevMonomer(firstMonomer)) {
-      firstMonomer = this.getPrevMonomer(firstMonomer)!;
+      firstMonomer = this.getPrevMonomer(firstMonomer) ?? firstMonomer;
     }
 
     const monomerChain = [] as BaseMonomer[];
     let monomerInTheChain = firstMonomer;
     monomerChain.push(monomerInTheChain);
     while (this.getNextMonomer(monomerInTheChain)) {
-      monomerInTheChain = this.getNextMonomer(monomerInTheChain)!;
+      monomerInTheChain =
+        this.getNextMonomer(monomerInTheChain) ?? firstMonomer;
       monomerChain.push(monomerInTheChain);
     }
     return monomerChain;