Me too. Nasty one! A single (very simple) database table (not sheet). The desktop version works fine, my phone can’t add records.
Killing the app and restarting didn’t clear 2 rows of data I had added either! Only an option to Cancel would bring up the app. I had to clear AppSheet data (cache alone didn’t work) on my phone for AppSheet - and of course lost the two updates I was trying to make. Viewing audit logs (very hard to read the last few long-strung together lines) didn’t tell me anything either, only that there were error from my phone app and not the desktop (added and deleted records fine there).
I’ve seen other responses about AppSheet Databases being in beta, beware!