I have also had issues in 3.5 with copy operations locking up the software. I had initially assumed it was an issue with our network or security software and didn't report it.
I have also had issues with selecting layers from the drop down menus in geoprocessing tools only to be told "the path contains spaces". Then if I navigate in file explorer to the same exact feature class it accepts it just fine.
I have also had issues with "jumping" when panning in an activated map frame within a layout. I suspect it has to do with it rendering or labelling.
For years I have had issues with annotation "vanishing" after being moved or the text being changed. Clearing cache and refreshing doesn't work. You can interact with the annotation in the new location but it isn't visible. You have to close and open the software again. Maybe that's similar to the issue you're having with other feature types now?
I would report more of these issues, but the last two times I filled out a support case online via Chrome, the textbox where you enter the details would lag as I typed. As in, I would type a sentence and then had to wait over a minute to see what I typed. It took me so long to submit the last case that I've given up. I mentioned the lagging in the support case and again in the survey but haven't heard anything. It's the box that says "powered by CKEditor" or something similar.