Negative spike bug?

I've recently installed my Empeg in a new (to me) vehicle, and it seems to be exhibiting some of the symptoms of the negative spike bug (forgetting song position, going straight into full off). This has me confused, as my player is a Mark 2a. Is it a known thing for the Mark 2a to exhibit the bug even though the diode that is supposed to solve the problem is already installed internally? Anything I can do about this?

It also could be a wiring problem, such as a blown fuse, or the power and ignition wires being connected wrong. Check that, too.

I forgot to mention that the problem is intermittent - maybe once every three or four times I shut the vehicle off for either problem. Could it still be the things you mentioned?

I won't have a chance to take apart the dash until this weekend, but thanks for the advice, I'll update on what I find.