Also be on the look-out for begin trans; begin trans; etc I read Kumar's report as nested transactions. If your gang is doing a transaction per row, they need a kick in the rear. Anyone not closing those needs a pink slip.
I have seen the second attempt at calling begin seem to be ignored with "WARNING: there is already a transaction in progress" similar to calling rollback without a transaction open. Are you stating or suggesting that calling begin a second time actually is more similar to creating a savepoint? That would be rather unexpected from the messaging, at least for me.
No. Hard to know what the devs are up to here (what stack they're using, etc), but I'm suggesting one transaction is getting started and not closed. Warnings have been know to be ignored. I admit I am not familiar with Kumar's term of "sub-transaction" and how those might be created but it sounds to me like a transaction is begun early in the processing and more work happens unaware of the transaction. And possible not committed.
