Thanks Lars, As an update, I see ETag.txt contains string which looks like timestamp in GMT Old= 20191210174535, new = 20191210174734; And this time represents the thumbnail download time, So you think it should be same every time? Or Etag should contain another unique value instead of timestamp string? Other file i see the same S3ECLProvider version in both files

Thank you Saurabh, TransactionCommitted phase of ProcessInstance suites my requirement. I have posted my working code as answer.

I can able to identify the event trigged by TM in this case with the help of your code. It is Save event - TransactionCommitted phase. I am not able to get debug event logs when it works.

@AntonM added event log to question above, Thanks!

Yes we are using Sticky sessions on LB @RickPannekoek