Apple music keeps renaming my playlists

We have a large number of playlists that end in numbers - e.g. best of 15 for the best of stuff we bought in 2015 or car playlist nos 1 through 8. Every so often my wife logs into her Mac to find that Apple Music seems to have renamed the playlist and changed one of the playlist names so that the number gets added to the end of the numerical sequence. Today, for example , we discoverd that car playlist 07 had been renamed to car playlist number 10 and best of 10 had been renamed best of 25. Why is it doing this and how do we stop it?

We have a lot of CDs uploaded, music purchased digitally and an apple music subscription, but we are old fashioned and only add music we have purchased to our playlists, not items from Apple music.