Hi!
Thank you for all the details, it helps us a lot.
Interestingly, it works on the back-end, so I am not completely sure about the cause of the issue. It might be another script conflicting as well, I can’t tell for sure. Anyways, I think the easiest possible solution is to use a custom code, that will force a ‘magnifier click’ whenever the return key is pressed.
Add this custom code to the functions.php in your theme/child theme directory (copy from line 3 only!). Before editing, please make sure to have a full site back-up just in case!
Make sure to clear the site cache afterwards. This should hopefully fix the issue.