New, annoying glitch

Hey,

I’ve been dealing with a new, very weird glitch. I’ve been working on my map, so I wanted to save 2 different versions of it.
But for some weird reason, nearly every grouped objects on the previous map will be grouped all together in the new version. It’s really weird.
And I’ve just noticed, that some parts of the map even totally disappeared in the new version. (I’ve checked it about 10 times now, I did nothing wrong.)
Obviously, this is game breaking and I can’t continue my work.

Does anyone else have the same issue?