[Pazuzu]

I've found that when the electrical part starts to go, you can get that intermittent start ability. Sometimes it involves wriggling the key and putting pressure on it to get it to "pop" over to the start location. It's gonna break soon. There is a lockout such that if you do get over to the start location, and then let it spring back, you cannot them put it back to start without completely shutting the car off. This is to prevent hitting the starter while the engine is running. That action is obvious when you do it, and it doesn't seem like it's what's going on with you, but I do think it's that same lockout assembly that is breaking internally and causing your issues.

The mechanical part of the switch is "dumb", and doesn't have any detents or anything, so it won't prevent the key from turning all the way over. Unless of course it physically breaks like my last one did, where the little pot metal "cross" that engages the electrical portion cracks off and jams in place, but you would have known already if something like that happened.