Ungrouped a large section of my collection

I have noticed another issue with my library. I noticed some artwork was missing since 880+. Managed to fix these by reidentifying the albums, but looking deeper it’s also ungrouped lots of titles that where previously grouped. Anyone else had this happen ?

I’ve only got 2 groups in my library and both survived 880!

I am wondering now if this might go back further to when they changed the versions tab grouping thing. I have not looked this deep for a while as the missing artwork made me look more closely. It’s not all of them either which is very odd.

So manually regrouping what’s got ungrouped. Got to L in my library and Roons slowed down to a point it’s unusable on Windows. Memory usage is excessive. So editing this amount of data is not making the app happy at all. Not had this before looks like some memory leak of some kind. Restart of app sorted it but this is annoying.