I have done several tests in my local and docker environment WP + MF and everything works fine. can you make some test with WP + MF same version with the conflict local o new instance in the server? if it works fine. can you put which plugins use on the site?. visit
https://github.com/hunk/Magic-Fields/issues/189 and put what plugins you use, I want to see which plugins you have in common.
another test, if you can, disable all plugins. enable MF and check if it works fine, next, enable one plugin and check, until all plugins are enabled. Optional you can download the site and test in local environment.