HP-41cx Card Reader rebuild question

[wheagy]

[attachment=1172]I'm rebuilding an HP-41 card reader due to the "gummy" deteriorated card feeder roller. It's working about 50%, but I'm having an issue, I think, with the part (small metal tab) outlined in red in this pic.
http://imgur.com/Q2QhwMy

This piece is flopping around somewhat loose and I'm not sure how it should fit. It appears to ride right above the read/write head when the unit is assembled, but I'm not sure if it's supposed to touch the head, hover just above it, or something else. When this part (metal tab) is in the plastic assembly, and I plug the reader into the HP-41cx, the reader motor immediately starts running, even with the HP-41 off, and eventually (after about 5 sec) just stops running. In this case it also will not allow the HP-41 to turn on either. If I leave the piece out of the plastic assemble - remove it), it seems to write a card, but when I try to read, I get a "CARD ERR" message. The piece does not appear to be electrically connected to any other part of the reader, so it seems like it might be for tension? But I'm not sure why the card reader mostly works when this piece is removed but not when it's installed.

Can anyone tell me the function of that part and how it should fit in the plastic housing?

Thanks,

Win