The node board upgrades have to allow for skipped versions. Otherwise, all the games shipping from the factory with 1.0 would have trouble upgrading to 1.20. So the node upgrades must be wrapped in the spk file.

But I agree about losing backwards compatibility... it looks like that is the case now, at least if nodes have been updated along the way.

That could be because your ball is bouncing out of the throne. The latest software will abort the mystery screen if that happens. I'd test it with the glass off and confirm. Then you could make some changes to the throne to catch the ball better if needed.

Can't speak to the rest of your issues.

yeah, if this is happening to people, then Stern needs to know about it so they can address it.

It seems to not affect everyone as my machine is playing fine.

Just speculation here on my part - but since the node board updates happen after you do a rom update AND power cycle the game... then it does the node update, I have to think that if you replace a node, that same update would happen on your next power cycle as it checked, and do so automatically with no other effort from you. That's what makes sense to me, i hope it's that simple.