fix error handling for non-replace situation to avoid hang

internal/mempool/mempool.go

@@ -231,6 +231,7 @@ func (txmp *TxMempool) removeExistingTx(res *abci.ResponseCheckTxV2) (bool, erro
 
 	// try to replace existing transaction in mempool
 	if existingTx := txmp.txStore.GetTxBySender(res.Sender); existingTx != nil {
+		fmt.Printf("mempool: priority=%d, new priority=%d\n", existingTx.priority, res.Priority)
 		if existingTx.priority >= res.Priority {
 			return false, types.ErrEvmTxNotReplaced
 		}
@@ -322,9 +323,11 @@ func (txmp *TxMempool) CheckTx(
 			txmp.logger.Error(
 				err.Error(),
 				"tx", fmt.Sprintf("%X", wtx.tx.Hash()),
+				"priority", res.Priority,
 				"sender", res.Sender,
 			)
 			txmp.metrics.RejectedTxs.Add(1)
+			return types.ErrEvmTxNotReplaced
 			// not treated as an error, fallthrough to callback
 		} else {
 			// log the replacement

internal/mempool/tx.go

@@ -1,6 +1,7 @@
 package mempool
 
 import (
+	"fmt"
 	"sort"
 	"sync"
 	"time"
@@ -311,18 +312,19 @@ func NewPendingTxs() *PendingTxs {
 	}
 }
 
-func (p *PendingTxs) RemoveSameEvmTxIfLowerPriority(resp *abci.ResponseCheckTxV2) (bool, error) {
+func (p *PendingTxs) RemoveSameEvmTxIfLowerPriority(res *abci.ResponseCheckTxV2) (bool, error) {
 	// lock needed so that indexes are fixed between search and delete
 	p.mtx.Lock()
 	defer p.mtx.Unlock()
-	for idx, tx := range p.txs {
+	for idx, existingTx := range p.txs {
 		// find the tx with the same nonce/address
-		if tx.checkTxResponse.IsSameAddressAndNonce(resp) {
+		if existingTx.checkTxResponse.IsSameAddressAndNonce(res) {
 			// only if it's lower priority than the new tx, replace it
-			if tx.checkTxResponse.IsLowerPriority(resp) {
+			if existingTx.checkTxResponse.IsLowerPriority(res) {
 				p.popTxsAtIndices([]int{idx})
 				return true, nil
 			}
+			fmt.Printf("pending: priority=%d, new priority=%d\n", existingTx.checkTxResponse.Priority, res.Priority)
 			// otherwise we must reject this transaction
 			return false, types.ErrEvmTxNotReplaced
 		}