As a DJ who has spent over 8 years building up playlists for all my gigs and genres this was a very frustrating problem to experience.
I found the best way to get round this was to invest more time into smart playlists and use tag words in the group section of the metadata to populate these playlists.
I've been doing this for about 3 months now and as my manual playlists keep randomly either emptying or have multiple tracks removed the smart playlists remain in tact, so far so good.
I've attached 2 images below which I hope will help those experiencing the same issue. As you can see the GROUPING column has various tags for my D&B sets and the smart lists on the right are set to look for:
- GENRE is Drum & Bass
- GROUPING contains [TAG WORD]