Clicking on buttons in editor windows not working without a resize

I'm having a weird issue with Unity right now where popup windows don't respond to button presses visibly - they appear not to repaint. I haven't changed anything that I can think of to have caused this.

This happens with the Console window - when I click Clear or any of the the other (toggle) buttons nothing happens unless I resize the window, then things appear to be fine until I reopen the window. The same thing happens with my custom editor window. I can get it to repaint once if I swap windows - when a window comes back into focus it seems to work.

I think maybe my custom editor is somehow causing this, but I really have no idea why.

Has anyone had anything like this happen? Should I just update Unity maybe?