Thank you for your post.
I found the ETS report, and it shows Testing was unable to reproduce the issue.
Previous tests do show that when you install a new version (not revision) of FileMaker Go, the Persistent ID will change.
This will be hard to proof prior to next FMGo16 update. This happened before during ETS with FMGo 126.96.36.199 and now happened again.
What we know so far is that iOS is creating a individual string within the iApp-Path which FMGo uses to build the PersistentID.
"Updating" a existing iApp should NOT alter PersistentID.
"Delete & Re-Install" any iApp will alter PersistentID any time.
If a FMGo update is based on a 'delete-old-and-install-new Version' routine, the PersistentID will alter.
Please ask Development for informations about differences between update routines where
- previous Version (latest ETS) to public FMGo188.8.131.52
- previous Version to FMGo184.108.40.206
and where PersistentID remained persistent
- all other FMGo16 updates during ETS16 period