Mp3tag freezes for x seconds when I try to change some tags

Let's say I have a list of 100 .mp4 and .mkv files and I want to change the "Comments" or "Rating" tag, for example. Every time I try to do that, the program freezes for about 30 seconds!!! Do you have any idea why this might be happening? And what can I do to fix it?

Thank you for your time!!!

have a look at this thread: