HP-65 more on the card reader

[albertofenini]

Hi Geoff,
thanks for your continuous help and support.
Yes, we are using read/write cards, un-clipped and even from different packages.
I also think that this consistent behavior across four different units, from different years can only be due to something trivial like a missing contact.
The question is, which one is the spring among the four that I have to check and more important
how can I check it given that once I reassemble the card reader the srping are hidden from the view ?
Thanks in advance !!

[Edit I] in all of the units, the springs are clean and the correspondent traces on the keyboard PCB are clean

[Edit II] I have attached a couple of diagramas (@moderator if this is some how inappropriate please remove the attachment)
These are for the CPU board and the card reader PCB.
I imagine that WA and WB stand for Write channel A, Write Channel B, as RA RB stand for Read Channel A, Read Channel B.
There is a GND pin for ground, a couple of Voltages.
There is then a WE pin, is this for Write Enable ?
I assume that if a card is recordable and the card protection switch works properly something must happen at this pin, right ?
What can I possibile expect and measure to see if the switch works ?
Is this pin normally open to ground and closes if the card is writable ?
Because the shape of the card is identical whether the card is protected or not
I assume that a non protected card will give as a first thing an "impulse" because of the presence of the upper left corner moving the switch
and this will the the CPU to enable the WA WB channels.
I'm missing however the scheme of the brass switches, which does what ?

Also in the scheme of the logic board the pin between WE and WB is marked as CRT/P while on the scheme of the card reader the same pin is marked ans N/C (Not Connected ?)

Thanks !!!