HP41 refuses to switch ON after some time OFF

[quantalume]

I had a 41CV fullnut with a similar problem which went away when I installed a new battery holder. I think the issue may have been creeping oxidation on the battery springs. Did you reuse the battery springs or get new ones?

Regarding the nuts, you should be safe if you are careful to engage the same threads rather than cutting new ones when you reinstall them. I have one 41C where one of the nuts was not tight enough from the factory. Removing the nuts, I could see that the threads weren't cut as far down on one side. You could check for this by pressing down on the CPU board and making sure there are no gaps between the board and nuts.