Reports about HP-41s ceasing operation or displaying strange characters for dropping, or no apparent reason at all, or recurrent MEMORY LOST episodes, start sounding familiar to me. A possible cause for this disorder is the lower (or proximal) of the steel spring rails (clamps) holding the display assembly, which shorts out several of the conductor traces on the top edge of the keyboard P.C. Such a short totally messes up the communication with the display controller and makes the HP-41 going crazy.
This was the case with my seemingly dead HP-41CV (SN 2117S11461). A piece of insulating tape applied to the lower display clamp rail perfectly cured the unit, which is now back in charge on my engineering desk.
For doing this repair, some minor surgery is inevitable however. The keyboard P.C. needs to be removed, or the display desoldered. I prefer removing the keyboard P.C. for this allows thorough cleaning of the keyboard and of the display at the same time. For dismantling and cleaning the keyboard (it is easier than it sounds), I will post detailed instruction if there is interest.
Luc