This bug is not specific to the latest version (3.10). It has happened to me with all previous versions, but this version does seem to be a little finicky.
The problem occurs when I am saving tags. It could be 15K tags or just 20, but if I have the audacity to click a file while the tags are saving 8/10 times the program will stop saving and just hang. It will not close and I have to force it closed with the task manager. It does not have to be one of the files that are currently saving, any file will cause this problem. And I am not doing anything other than just selecting it. This is not a case of trying to play the file or edit the tags. Just selecting the file crashes the program.
Another thing I have noticed with this version is that in Dark Mode, sometimes files will change colors while saving, but as soon as I sweep the mouse over them, they switch back from white (or light grey) to black background. This is not that important but I thought I would include it.
I will check soon. I have yet to update. I have 15k files loaded at the moment. I will try later tonight and report back. It takes a while because I want all the files to load before reattempting to recreate the error. You have been busy with the updates. I guess it is time to send some more "support" your way.
Unfortunately I have to report that this is still occurring. I just downloaded 3.11 and installed it. I loaded just 311 files. I highlighted 68 of them and hit save. As it was saving I clicked on random files (just one click, no double clicking) and after click the second or third I got a Runtime Error. This has been occurring for some time using several different versions of Mp3Tag. At one point it did not happen but I am not sure when. This will always happen if I click on any file line in mp3Tag while it is saving. Hopefully this can be resolved.