@Dhanalakshmi I think you are asking me, since I got notified of this reply.
The answer is this:
To elaborate, this means that you need to do a thorough audit of any BPM or function that you have ever made, if it creates part transactions, and then add the deferred update code to the end of it.
(Of course, I also mean any code that others in your organization have made, even if you made it years ago.)
Now, what tripped me up was that the Function that was messing everything up was to report labor. Is that a part transaction? Yes and no. It’s not directly, but because I was reporting quantity, that resulted in material backflush. So I added deferred update to it and we have been fine since. We have done hundreds of thousands of transactions since then without a problem.
BUT if you nor your co-workers (past and present) have never ever used deferred update anywhere, then ignore everything I have said.