Updsted my app to the latest version on Sunday after being in the field for two weeks without issues. Since the update the app restarts itself every minute or so. Very frustrating and comcerning. Had to abandon a paid job today as a resukt and return another day. Samsung Galaxy S2 tab, as mentioned was working fine for last two weeks flying every day.

Hello, Sir, please help to verify that your current DJI Go 4 APP version is V4.1.18 right?
Did you try to install the APP, please note to do a backup like syncing the flight record and saving the pictures and videos before your re-installation.
If the problem persists, please export the crash log for further analysis, which can be found in /DJI/dji.go.v4/LOG/CRASH.
Once you get it, please upload to Dropbox or Google Driver and post the link here, thank you.

Ok I will try a full re-installation of the app, and report back.