Unity is really slow when selecting.

Hi everyone!

The Problem:

I've been working on a game for several years now, and unity seems like a really stable and well build engine. - I've run into very few errors that I couldn't solve, some time ago (Probably about a month) Unity started to get pretty slow. The editor runs smoothly enough, and I achieve normal framerates in my game, but whenever I select something in the editor, like a object in the scene or hierarchy, A asset in the Project tab, or opens up the Input settings everything freezes for about 5 seconds.

This is obviously really annoying, and I really hope that someone knows how to fix it. I have found no solutions on the internet though, and I also haven't found any myself. I have found though, from profiling the editor that "EditorApplication.Internal_CallUpdateFunctions" is what takes up 99,7 percent of the performance in that frame. This is categorized as garbage collection by unity.

It's worth noting that this happens in any scene in that project, even an empty one. Also note that this only happens in this project.

What I've tried

• Copy the project to a different directory

• Reimport all assets

• Reorganize both the hierarchy and project window (Not likely to fix the problem, but it had to be done anyway)

• Close all tabs except the project tab

• Advance profile the editor to see what specific functions are called (Advance profiling doesn't even pick up the 5 second freeze)

I really hope that my issue can be resolved. None the less Thank you. :)

Edit:

I forgot to mention, that if I select an object, then deselect it, and then select it again the selection happens immediately.