PC (the core) was dead slow in ROON but OK now - what causes this problem and how to fix it next time?

This is a generally fast PC with heaps of memory but recently was very sluggish in Roon.

What fixed it was removal of a rogue music file when deleting duplicates but I’m unsure which file was the culprit and how/why it caused the problem so would appreciate advice from more PC educated Roonophiles.

Something I came across was the odd set of album files Roon refused to delete so I deleted them in File Explorer (dangerous I know, but I have backups of the music files in case of stupid errors). So maybe that is a hint to what was going on? Why does Roon refuse to delete an album?

Bottom line is I’m as generally happy Roon camper and appreciate all the effort going into it :slightly_smiling_face: