Same thing happens to me after a few hours of editing. Shutdown the app and reopen problem should be fixed. You may need to restart the computer
These bugs frustrate me cause I honestly dont see them myself.
But I have witnessed them on friends and students with varying workstations.
I submitted one funky bug to Apple weeks ago that confused the heck out me.
Hoping that it will all be fixed in the next update
Yep all the bad ones are gone for me as well.To be fair the problem posted by the OP was an issue for me around September last year... since then Apple has released a couple of updates and the problem hasn't come back.