Exception: Serialization of 'Closure' is not allowed in serialize()

Since updating to 1.0.3 we are seeing fatal errors when updating/creating users. (1.0.2 works fine)
We are running Drupal core 11.1.8

Exception: Serialization of 'Closure' is not allowed in serialize() 

This error only occurs when we add an image field, using the media library widget to the user. (might be other use cases, don't know)

We "fixed" the error by commenting line 59 in FormHooks.php:

        $form['actions']['resend_register_mail']['#submit'][] = [$this, 'submitForm'];

This causes the module to not work anymore though, so not an actual solution...

Related to: https://www.drupal.org/project/resend_register_mail/issues/3519847