I would not expect your cluster problems to be related to the 5 spd.

The needle has a return spring that is not very robust, for obvious reasons, and my guess is that the needle just gets stuck.

That's the approach I would take if I was faced with this. My instinct, wrong as it is sometimes, is that the cluster has been serviced with WD40, and now it is "glued shut". One test for this would be to push the engine above 4K and then observe if the needle falls back slowly or quickly. If slow then the mechanism is gooey and a cleaning is in order. Consider that the lamps burn out and the display goes dark as a result. A previous owner went in to replace some bulbs and decided, "this would be a good place to spray something." Then you bought the result. That's my guess.