I’d like to recommend looking at a couple of specific examples of tracks that did not get imported into Roon. Are they supported files? Are they showing up in Skipped Files? If it looks like they should be importing, let me know! Screenshots of these files in their storage location would be helpful for discovering what may be happening.
I had a look at the why some files might be missing from Roon, no positive results from there as well.
I am pretty sure most of the files in those directory are supported. I can copy of some folders and put those folders in a TEST ROOT to test. Would you like me to do that ?