I do not think that there is a limit of just a hundred files. It goes well into the tens of thousands when loading.
Why do you think there is such a limit?
I do not think that this is an MP3tag problem but much more something that has to do with your local hardware and other pieces of equipment.
Also: simultaneously running processes like indexers, other media players that check their watched folders, cloud synchronization could effect this.
See if there is anything you can optimize .
There must be going on something evil on your machine.
I have just created 2000 mp3 files with tag types (ID3v1 ID3v2.4), with no covers embedded, stored into 100 folders.
On a Win XP machine with 1 Ghz-Pentium-3 Processor it needs 20 seconds, ...
to save the folder name into the ALBUM tag-field.
Tagging on 4000 mp3 files with tag types (ID3v1 ID3v2.4), with no covers embedded, stored into 200 folders, on same machine, on different drive, runs 90 seconds.
Yep - must be something evil but hey - it took a little longer. I'm retired, busy doing nothing and just pleased I got it done far faster than I anticipated.