Issue with creating / editing emails - Mautic 5.2.0

Great, then this problem pre-dates your current update, and thankfully we’ve had folks reporting that problem on the forums before, eg How to update 5 to 5.0.1 via composer? - #7 by escopecz.

Give that a shot (of course, making sure you have a good database backup) to see if that fixes the pre-existing issue with migrations.