diff --git a/packages/taiko-client/driver/txlist_fetcher/calldata.go b/packages/taiko-client/driver/txlist_fetcher/calldata.go
index 7beee95e99b..9f8de41548e 100644
--- a/packages/taiko-client/driver/txlist_fetcher/calldata.go
+++ b/packages/taiko-client/driver/txlist_fetcher/calldata.go
@@ -52,5 +52,9 @@ func (d *CalldataFetcher) Fetch(
 		return iter.Event.TxList, nil
 	}
 
+	if iter.Error() != nil {
+		return nil, fmt.Errorf("failed to fetch calldata for block %d: %w", meta.GetBlockID(), iter.Error())
+	}
+
 	return nil, fmt.Errorf("calldata for block %d not found", meta.GetBlockID())
 }
diff --git a/packages/taiko-client/pkg/chain_iterator/event_iterator/block_proposed_iterator.go b/packages/taiko-client/pkg/chain_iterator/event_iterator/block_proposed_iterator.go
index 67fc0fea23d..be350e5aeeb 100644
--- a/packages/taiko-client/pkg/chain_iterator/event_iterator/block_proposed_iterator.go
+++ b/packages/taiko-client/pkg/chain_iterator/event_iterator/block_proposed_iterator.go
@@ -111,16 +111,6 @@ func assembleBlockProposedIteratorCallback(
 	) error {
 		endHeight := end.Number.Uint64()
 
-		iter, err := taikoL1.FilterBlockProposed(
-			&bind.FilterOpts{Start: start.Number.Uint64(), End: &endHeight, Context: ctx},
-			filterQuery,
-			nil,
-		)
-		if err != nil {
-			return err
-		}
-		defer iter.Close()
-
 		iterOntake, err := taikoL1.FilterBlockProposedV2(
 			&bind.FilterOpts{Start: start.Number.Uint64(), End: &endHeight, Context: ctx},
 			filterQuery,
@@ -130,26 +120,6 @@ func assembleBlockProposedIteratorCallback(
 		}
 		defer iterOntake.Close()
 
-		for iter.Next() {
-			event := iter.Event
-
-			if err := callback(ctx, metadata.NewTaikoDataBlockMetadataLegacy(event), eventIter.end); err != nil {
-				return err
-			}
-
-			if eventIter.isEnd {
-				endFunc()
-				return nil
-			}
-
-			current, err := client.HeaderByHash(ctx, event.Raw.BlockHash)
-			if err != nil {
-				return err
-			}
-
-			updateCurrentFunc(current)
-		}
-
 		for iterOntake.Next() {
 			event := iterOntake.Event
 
@@ -170,6 +140,6 @@ func assembleBlockProposedIteratorCallback(
 			updateCurrentFunc(current)
 		}
 
-		return nil
+		return iterOntake.Error()
 	}
 }
diff --git a/packages/taiko-client/pkg/rpc/methods.go b/packages/taiko-client/pkg/rpc/methods.go
index 824eaceaae6..6ce4278dd81 100644
--- a/packages/taiko-client/pkg/rpc/methods.go
+++ b/packages/taiko-client/pkg/rpc/methods.go
@@ -74,6 +74,9 @@ func (c *Client) ensureGenesisMatched(ctx context.Context) error {
 		if iter.Next() {
 			l2GenesisHash = iter.Event.BlockHash
 		}
+		if iter.Error() != nil {
+			return iter.Error()
+		}
 	} else {
 		// Fetch the genesis `BlockVerified` event.
 		iter, err := c.TaikoL1.FilterBlockVerified(filterOpts, []*big.Int{common.Big0}, nil)
@@ -84,6 +87,9 @@ func (c *Client) ensureGenesisMatched(ctx context.Context) error {
 		if iter.Next() {
 			l2GenesisHash = iter.Event.BlockHash
 		}
+		if iter.Error() != nil {
+			return iter.Error()
+		}
 	}
 
 	log.Debug("Genesis hash", "node", nodeGenesis.Hash(), "TaikoL1", common.BytesToHash(l2GenesisHash[:]))
@@ -836,6 +842,9 @@ func (c *Client) GetTaikoDataSlotBByNumber(ctx context.Context, number uint64) (
 	for iter.Next() {
 		return &iter.Event.SlotB, nil
 	}
+	if iter.Error() != nil {
+		return nil, fmt.Errorf("failed to get state variables by block number %d: %w", number, iter.Error())
+	}
 
 	return nil, fmt.Errorf("failed to get state variables by block number %d", number)
 }