diff --git a/go/vt/vttablet/tabletmanager/vreplication/replicator_plan.go b/go/vt/vttablet/tabletmanager/vreplication/replicator_plan.go
index aee7f5c8909..caee2f9ed04 100644
--- a/go/vt/vttablet/tabletmanager/vreplication/replicator_plan.go
+++ b/go/vt/vttablet/tabletmanager/vreplication/replicator_plan.go
@@ -620,6 +620,10 @@ func (tp *TablePlan) appendFromRow(buf *bytes2.Buffer, row *querypb.Row) error {
 		return vterrors.Errorf(vtrpcpb.Code_INTERNAL, "wrong number of fields: got %d fields for %d bind locations ",
 			len(tp.Fields), len(bindLocations))
 	}
+	if len(row.Lengths) < len(tp.Fields) {
+		return vterrors.Errorf(vtrpcpb.Code_INTERNAL, "wrong number of lengths: got %d lengths for %d fields",
+			len(row.Lengths), len(tp.Fields))
+	}
 
 	type colInfo struct {
 		typ    querypb.Type
diff --git a/go/vt/vttablet/tabletmanager/vreplication/vcopier_atomic.go b/go/vt/vttablet/tabletmanager/vreplication/vcopier_atomic.go
index 3a0996e0c39..1e3892c0f05 100644
--- a/go/vt/vttablet/tabletmanager/vreplication/vcopier_atomic.go
+++ b/go/vt/vttablet/tabletmanager/vreplication/vcopier_atomic.go
@@ -84,6 +84,11 @@ func (vc *vcopier) copyAll(ctx context.Context, settings binlogplayer.VRSettings
 	defer rowsCopiedTicker.Stop()
 
 	parallelism := int(math.Max(1, float64(vc.vr.workflowConfig.ParallelInsertWorkers)))
+	// For now do not support concurrent inserts for atomic copies.
+	if parallelism > 1 {
+		parallelism = 1
+		log.Infof("Disabling concurrent inserts for atomic copies")
+	}
 	copyWorkerFactory := vc.newCopyWorkerFactory(parallelism)
 	var copyWorkQueue *vcopierCopyWorkQueue
 
@@ -154,7 +159,7 @@ func (vc *vcopier) copyAll(ctx context.Context, settings binlogplayer.VRSettings
 
 			lastpk = nil
 			// pkfields are only used for logging, so that we can monitor progress.
-			pkfields = make([]*querypb.Field, len(resp.Pkfields))
+			pkfields = make([]*querypb.Field, 0, len(resp.Pkfields))
 			for _, f := range resp.Pkfields {
 				pkfields = append(pkfields, f.CloneVT())
 			}