"That doesn't make any sense, it's running the same code in the same browser engine."
I agree. Since it's a toxic bug (with no solid steps to reproduce) and, as far as i can see, it only affects a limited number of users, my best bet is to wait for another stable release to properly retest it.
Meanwhile, since i am unlucky enough to be affected, i will stick to any workaround that actually works, even if it makes no sense.
My wild guess is that the editor can grey out or hang if there is a considerable ammount of events and objects in it. E.g. my current game is 4000+ events and 900+ objects.
Anyways, i will get back to reproducing it with the next stable C3 version.