Queued sync with external DJ as repo stopped working before all users were synced

Using external DJ as repo, with sync and queued sync enable, the test preload 2400 users to IDM, the users were all synced to external resource(DJ), when more(124051) users were created, only 1398 users were synced to DJ, then nothing happened after that with one hour time lapse.

Didn't see any error in IDM or DJ logs(IDM logs attached)

To reproduce it using pyforge:
1. Used the config attached.

2. Run the command:

run-pybot.py -v -c perf -s implicit_sync.IDMDJImplicitSyncCreateSyncTime OpenIDM 

3. watch pyforge debug.txt for the progress and see the symptom

Note:

1.The symptom doesn't occur when MySQL or Postgres are used as repo.

2. The symptom occurred for all create/update/delete sync operations

3. The symptom was not seen in IDM 6.5.0