Q: iTunes purchased music removed from playlists into "Purchased" list

Two weeks ago, I noticed that a bunch of my iTunes purchased music disappeared from my Album playlists that I create for each new album I buy.  I restored my iTunes library using a 3rd party program and it was fine.  Fast forward to today, and I notice the problem again.

I finally figured out that the file paths were removed from the individual playlists into the Purchased folder in iTunes.  I'm thankful the files are still there, but I'm very frustrated as to why all of my purchased music suddenly consolidated into the Purchased folder.

Does anyone have experience with the above, as well as a possible solution to prevent it from occurring?  I could manually place these files back into their individual playlists, but I don't want to waste my time if on the next sync the files will just end up back only in the Purchase folder.

Many thanks.