Push rods coming loose

63 Dart original engine

So I went to start the dart and the battery was dead. I left the lights on.:banghead:
I charged the battery.

The car started but sounded rough and there was a lot of valve train noise and it was missing. It sounded fine and quiet the day before.

I pulled the valve cover and the number 6 exhaust push rod was no longer touching the rocker arm. It wasn't bent or damaged in any way and the rocker was not out of adjustment it was just off. So I re-installed the push rod and readjusted the all of the rockers.
I let the car idle until the car was up to temp and then set the intake to 10 thousandths and the exhaust to 20 while the engine was idling.

it sounded great, I shut the engine off.

5 hours later I went to start the car and it was missing again. I pulled the valve cover and now the number 4 exhaust push rod was disconnected. I repeated the procedure above and then immediately drove the car, it is fine now but I haven't let it cool down to try it again.

So WTH :banghead:

I checked the timing with a light and it is fine.