Not really since i'm having a similar issue.
Processing beatmaps or the F5 function isn't working properly as intended atm.
I deleted A LOT of taiko maps in my database through win explorer (songs folder) but after hitting F5 in the beginning and all maps where processed, Taiko maps are still being listed.
Whenever you click on one: "Beatmaps are being processed..."
At the end: 1 map has been removed. (the one you clicked)
Although the others are still being listed while they aren't available anymore on your HDD/SSD.
This is quite frustrating with my 70GB songs database w/o taiko maps
Deleting map types/diff from within osu! goes faster rather than doing it by explorer due this (although it shouldn't)
Seems like the "Beatmaps are being processed..." thingy only looks at the current selected map trying to search for it, while F5 doesn't really compare it within the folder, just folder name.
But I'm going to try the renaming of the osu!.db and see if it helps rebuilding the whole database from scratch.
I just hope that it won't look just at folder names but also at it's contents.
EDIT: Ok, it's fine for me now, thx
But I gotta say that this is a very bold way to fix this