Deleting Songs in Set Lists - possible bug

Multiple existing setlists are getting truncated when I remove songs from a project to create a new shorter list.

I have created a project to use to store my songs for this year, 15 in total. I’ve saved this as a set list. When I want to create a smaller set from this list, I delete the songs not required and save as a new set list, e.g, Gig1.
To create another set for a different gig, I reload the full list, delete some different songs and save this as a new setlist named Gig2.
I have 5 or 6 different set lists now, with varying numbers of songs.

After saving the project, then reloading VST live another time, all looks ok when it loads up. However, as soon as I move to a shorter set list, songs start disappearing from all the set lists. If gig1 has 7 songs, next time I click on the full set list, it also has only 7 songs. The original 15 have been truncated.
I have to restore the project from my backups to get my songs back.

There is something more going on that simply truncating to the shortest list. I have tried testing this a few times to work out if I was doing something wrong. On one test I created a small list of 2 songs, one list with 11 songs and 3 lists with 15. After saving and reloading, I had some lists with 2 songs, some with 6 but none of the longer lists had more than 6.

I am running the latest v1.1.80. This behaviour has been there since v1.1.60 at least.

We are still looking into this, sorry it takes a while, will report back.