Hi David,

here is another thought - and I will check it on my A4: The valve clearance might be too tight. Now, if the engine heats up, the valves become longer and therefore won't shut anymore. The engine cools down and the problem is gone.
I don't know the exact valve clearance - someone might know it.

Let me know if you get a step forward. I have no chance to get to my Catalina before spring.

Regards,
Chris