Another possibility is a loose battery connection or bad ground wire. If your emergency start switch is working correctly, it should have started your engine. You can check that with a volt meter by seeing if your chassis battery increases in voltage when the emergency start switch is pushed. If it happens again, you might try holding down on the emergency switch for several minutes and let the chassis battery come up some before you attempt to start it with the emergency switch pushed in. Your truck with the engine running is putting out close to 14v while your coach batteries only add 12+ volts. So it may be able to overcome a bad battery cell or connection.
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