Loading multiple M4a files into MP3Tag hangs

Hi
Have just converted approx 65k tracks from FLAC to M4a to load into iTunes/Apple Music.
Now trying to load ALL 65k M4a tracks into MP3Tag and it counts them up and then hangs when it gets to the last one - ie they never appear in the main MP3Tag window.
The window that was counting them up now says Reading Directory (Not Responding). In the window it says "Reading tag data ... 64369 of 64369". I have tried this twice and same both times.

I have done this many times before with this volume of MP3s and FLACs and never had any problem. In fact I have just tried loading same volume (approx 65k) of MP3s and then separately FLACs and no problem with either.

I can load individual tracks and an album of M4a's - but it seems to have a problem above a certain volume of tracks. Any ideas what is wrong?

Thanks
G

Have you activated the Library function in
Tools>Options>Library
?