HP-41C - serial 2052A - Memory Lost

[Vintage63]

Good day to you all, I'm back here after some time. I nevere finished repairing the clutch mechanism on my old card reader, but every now and then have a look at it.

My current problem, maybe solved for now, is the following. I had 3 memory modules. Every time I inadvertently 'banged' the calculator on the desk it froze and I had to remove the batteries to try and get it to work again. Obviuosly the dreaded Memory Lost popped up on the screen.

I rotated the memory modules in the bays and banged on purpose the 41C until it stopped freezing.

Thinking I had finally found a safe position I rewrote the various programs I kept losing.

It did it again yesterday evening. So the rotation wasn't succesful. I tried again by inserting and banging the thing until I found out that it froze with one module only. I removed it from the slot and put away.

QUESTION: is this normal, banging and freezing, or is there something I can check on the memory module to stop this from happening again, maybe the pins on the back? Or my 41C has reached the end of its life?

NB banging means placing it back on another of the desk locations without being too careful.
Thank you
Marco