Resolved

I have managed to resolve this issue thanks to my colleague Rich, who linked me to this answer

I’ve recently been using an iPad much more frequently than I have in the past and during this time my frustration over swipe actions in mail has grown into all consuming anger.

Swipe actions in all apps but especially when triaging mail should be the simplest, muscle memory function that can exist with touch devices. Instead I have to double check I am swiping the right way every time.

For my iPad, I have to swipe right but on my iPhone I need to left.

Configuration

As you can see both devices are set up to archive on swipe right and both are linked to the same fastmail email account.

iPad config iPad configuration

iPhone config iPhone configuration

Result

Here you can see that the results are different.

iPad swipe right (correct) iPad swipe right shows archive option correctly

iPad swipe left (correct) iPad swipe left does not show archive as expected

iPhone swipe right (incorrect) iPhone swipe right does not show archive option

iPhone swipe left (incorrect) iPhone swipe left shows archive when it is not expected to

I have searched and searched but not been able to find the answer. Please contact me if you know the answer.