delta sync on top of a deletion caused data discrepancy between SG and CBL

NOTE: Conflict Resolver was not the cause of this issue. 

Steps to reproduce:
1. Create docs in CBL.
2. Replicate docs to SG with push_pull and continuous False
3. Wait until replication is done and stop replication
4. Update docs in SGW and delete docs in CBL in parallel (multithreading)

   or delete docs in SGW and update docs in CBL in parallel(multithreading)
5. Start the replication with same configuration as step 2
 
Expected :
6. Verify docs get deleted in CBL/SGW
 
Actual:
Docs  still exists in CBL/SGW
 
Logs :
log_1560910929.93239.zip
 
Tested with no-conflicts enabled/disabled and I see same issue.