I've made a backup, and tried copying older backup files into the backup I just made, and then tried out that data. Nothing happened.

I then re-named the 4 files in the backup, and tried again. The statement group tree is now available, but none of the actual groups I had are available - i.e. I can set up new groups, and have to start from scratch.

I have also tried to replace each file - one at a time.
My existing groups do not seem to come back, although I do get access to the tree.