Issue is only reported on Base version of 6.6 and is already fixed in the latest branch of iVend release available for the production use.
Steps if any: Below are the step we require to follow-up to resolve the issue.
1.Extract the data against table InvStockTransferRequest on Enterprise database where id is null.
2.Update the id same as request number if same id already exists then amend -1 on request number
3.Generate the replication events against updated InvStockTransferRequest