diff --git a/source/dnode/mnode/impl/src/mndSubscribe.c b/source/dnode/mnode/impl/src/mndSubscribe.c
index 739b8bbf01b0f4a871d611e34729363097ca1d92..eea79c533584d7aede84b834ce568500a22afe12 100644
--- a/source/dnode/mnode/impl/src/mndSubscribe.c
+++ b/source/dnode/mnode/impl/src/mndSubscribe.c
@@ -550,7 +550,7 @@ static int32_t mndPersistRebResult(SMnode *pMnode, SRpcMsg *pMsg, const SMqRebOu
 
   // 6. execution
   if (mndTransPrepare(pMnode, pTrans) != 0) {
-    ASSERT(0);
+    mError("failed to prepare trans rebalance since %s", terrstr());
     goto REB_FAIL;
   }
 
diff --git a/source/libs/wal/src/walRef.c b/source/libs/wal/src/walRef.c
index 2c45fbbdaf3148ea194a09c31c97b13d7b6d31ec..119d0575d8959e8657deef7f6109c5d6d6623a81 100644
--- a/source/libs/wal/src/walRef.c
+++ b/source/libs/wal/src/walRef.c
@@ -42,6 +42,7 @@ void walCloseRef(SWal *pWal, int64_t refId) {
 
 int32_t walRefVer(SWalRef *pRef, int64_t ver) {
   SWal *pWal = pRef->pWal;
+  wDebug("vgId:%d, wal ref version %" PRId64 ", refId %" PRId64, pWal->cfg.vgId, ver, pRef->refId);
   if (pRef->refVer != ver) {
     taosThreadMutexLock(&pWal->mutex);
     if (ver < pWal->vers.firstVer || ver > pWal->vers.lastVer) {
diff --git a/source/libs/wal/src/walWrite.c b/source/libs/wal/src/walWrite.c
index 3354308c497a88ed5d0cb0a86573edc488f61b7a..e6b4e9d8ff576b42b68047f190624eca1da934cb 100644
--- a/source/libs/wal/src/walWrite.c
+++ b/source/libs/wal/src/walWrite.c
@@ -257,6 +257,8 @@ static FORCE_INLINE int32_t walCheckAndRoll(SWal *pWal) {
 
 int32_t walBeginSnapshot(SWal *pWal, int64_t ver) {
   pWal->vers.verInSnapshotting = ver;
+  wDebug("vgId:%d, wal begin snapshot for version %" PRId64 ", first ver %" PRId64 ", last ver %" PRId64,
+         pWal->cfg.vgId, ver, pWal->vers.firstVer, pWal->vers.lastVer);
   // check file rolling
   if (pWal->cfg.retentionPeriod == 0) {
     taosThreadMutexLock(&pWal->mutex);
@@ -273,6 +275,10 @@ int32_t walEndSnapshot(SWal *pWal) {
   int32_t code = 0;
   taosThreadMutexLock(&pWal->mutex);
   int64_t ver = pWal->vers.verInSnapshotting;
+
+  wDebug("vgId:%d, wal end snapshot for version %" PRId64 ", first ver %" PRId64 ", last ver %" PRId64, pWal->cfg.vgId,
+         ver, pWal->vers.firstVer, pWal->vers.lastVer);
+
   if (ver == -1) {
     code = -1;
     goto END;
@@ -287,7 +293,8 @@ int32_t walEndSnapshot(SWal *pWal) {
     if (pIter == NULL) break;
     SWalRef *pRef = *(SWalRef **)pIter;
     if (pRef->refVer == -1) continue;
-    ver = TMIN(ver, pRef->refVer);
+    ver = TMIN(ver, pRef->refVer - 1);
+    wDebug("vgId:%d, wal found ref %" PRId64 ", refId %" PRId64, pWal->cfg.vgId, pRef->refVer, pRef->refId);
   }
 
   int          deleteCnt = 0;
@@ -298,8 +305,9 @@ int32_t walEndSnapshot(SWal *pWal) {
   SWalFileInfo *pInfo = taosArraySearch(pWal->fileInfoSet, &tmp, compareWalFileInfo, TD_LE);
   if (pInfo) {
     if (ver >= pInfo->lastVer) {
-      pInfo++;
+      pInfo--;
     }
+    wDebug("vgId:%d, begin remove from %" PRId64, pWal->cfg.vgId, pInfo->firstVer);
     // iterate files, until the searched result
     for (SWalFileInfo *iter = pWal->fileInfoSet->pData; iter < pInfo; iter++) {
       if ((pWal->cfg.retentionSize != -1 && newTotSize > pWal->cfg.retentionSize) ||
@@ -315,10 +323,12 @@ int32_t walEndSnapshot(SWal *pWal) {
     for (int i = 0; i < deleteCnt; i++) {
       pInfo = taosArrayGet(pWal->fileInfoSet, i);
       walBuildLogName(pWal, pInfo->firstVer, fnameStr);
+      wDebug("vgId:%d, remove file %s", pWal->cfg.vgId, fnameStr);
       if (taosRemoveFile(fnameStr) < 0) {
         goto UPDATE_META;
       }
       walBuildIdxName(pWal, pInfo->firstVer, fnameStr);
+      wDebug("vgId:%d, remove file %s", pWal->cfg.vgId, fnameStr);
       if (taosRemoveFile(fnameStr) < 0) {
         ASSERT(0);
       }
@@ -409,7 +419,7 @@ END:
 }
 
 static int32_t walWriteIndex(SWal *pWal, int64_t ver, int64_t offset) {
-  SWalIdxEntry entry = {.ver = ver, .offset = offset};
+  SWalIdxEntry  entry = {.ver = ver, .offset = offset};
   SWalFileInfo *pFileInfo = walGetCurFileInfo(pWal);
   ASSERT(pFileInfo != NULL);
   ASSERT(pFileInfo->firstVer >= 0);
@@ -424,7 +434,8 @@ static int32_t walWriteIndex(SWal *pWal, int64_t ver, int64_t offset) {
     return -1;
   }
 
-  ASSERT(taosLSeekFile(pWal->pIdxFile, 0, SEEK_END) == idxOffset + sizeof(SWalIdxEntry) && "Offset of idx entries misaligned");
+  ASSERT(taosLSeekFile(pWal->pIdxFile, 0, SEEK_END) == idxOffset + sizeof(SWalIdxEntry) &&
+         "Offset of idx entries misaligned");
   return 0;
 }
 
@@ -432,7 +443,7 @@ static FORCE_INLINE int32_t walWriteImpl(SWal *pWal, int64_t index, tmsg_t msgTy
                                          const void *body, int32_t bodyLen) {
   int64_t code = 0;
 
-  int64_t offset = walGetCurFileOffset(pWal);
+  int64_t       offset = walGetCurFileOffset(pWal);
   SWalFileInfo *pFileInfo = walGetCurFileInfo(pWal);
   ASSERT(pFileInfo != NULL);