Batch editing performance issues on NAS

Hi Guys,
Been a happy user of MP3Tag for a while now.
Have run into a very odd problem when doing batch editing of files:
I wanted to re-categorize all the music on my NAS drive - approx. 25,000 files across 7 major music genres.
I do a select, grab say 500 files, mark say 50 files and change the Genre to e.g. Classical.
First batch fine - takes about 15 seconds or so for 50 files. The next 2-5 batch same thing, and then - while still working on files in the same sub-dir - all tag writing suddenly then takes 20 times as long, in the order of 10 minutes for 50 files. This will continue until I close MP3Tag, and restart the app.
Why? All files are located in the same shared directory structure; no network issues; same number of tags being edited; oh, and I have tried to sort the selection by sub-dir, artist etc - makes no difference.
Is there anything that I am missing here?

Bo P

Slow access because ...

  • network connections are the almost the slowest way to access a lot of files,

  • other processes like indexers, players, anti-virus programs could block the files for some time,

  • padding is not big enough so the files have to be rewritten,

  • Windows Defender slows down the access, see e.g.
    Windows Defender - Speed of loading files in MP3Tag

  • File sizes vary (e.g. is bigger for some files than for others) and together with insufficient padding lead to re-writing the big files - which takes longer.
    These would be the knobs I would twiddle and tweak.

in addition:
Be aware of not using wifi, even it's seems to be "fast".
Performance issue on batch processing (backup, mp3tag, mediapurge, what ever) slow down extremely