Jiggling the key will NOT have any effect on your problem. The key is connected to the ignition switch by a long rod. The ignition switch is under the dash on top of the steering column. Check that connection.
In most automotive applications the alternator will keep the engine running without the battery BUT you coach has a chassis battery disconnect relay. If your alternator charges the battery and the disconnect relay fails when you hit a bump, your engine dies.
Move all the large wires on the disconnect relay to one terminal and see if the problem goes away. Disconnect relay is in the Battery Control Center. Wiring schematic in inside of BCC cover.
Richard