Hi,
We were finally able to reproduce the access violation. We have further investigated this here and went back to basics. We added an Edit to a styled Panel with inside the Panel a TRectangle (to simulate what happens in TTMSFMXTableView). Basically as soon as the edit is added, the edit is destroyed on iOS. You can try it out with the following sample.
Sample.zip (10.1 KB)
You'll notice Edit1 is destroyed and no longer accessible, when clicking on Button1, you get an access violation. This is what also happens on TTMSFMXTableView. This must be something new related to the following fix they applied: Log in - Embarcadero Technologies, although we are not 100% sure that it is a bug they introduced by applying this fix, or if it's a new bug altogether. Either way, as we isolated this in a new FMX project without FMX components, it's clearly an FMX framework/Delphi 12 issue.
I've went ahead and created a bug report via Embarcadero QC
https://quality.embarcadero.com/browse/RSP-43965
Unfortunately right now, it's unclear if we can get a hotfix or a fix in Delphi12, we tried several things to workaround it without success.