Session is already locked - Causes instability

[reallyethical]

I can't answer your question, but I'm certain those who can will want to know your IW version and Delphi version.  Some of those will be just starting their day soon.  It may save some time if you can post that and any other info about context (recent changes, etc) and whether you can force the error at will.

Dan

IW 15.2.3
Delphi Seattle