HI;
I have an HP55 with a "soft-to-touch" reaction, like you described. But I opened the calcualtor and saw a small crack in the upper part of the keyboard's contact, a bended metal sheet. It lost the preassure because of this, and the only way to fix it is to remove and sold another. If it finally breaks sometime, I'll do that.
In the HP41's keyboard there are small caps, like part of a sphere surface. If these caps also have cracks, they will be soft for touch as well. In this case, the replacement is not hard, provided you find a "donator".
AND the other possibility is the rubber sheet over the keyboard. The point-of-touch of each key is a small bar in the HP41's keys, and if the rubber tears off at the touching surface, the rubber will hold the key and soften the "key feeling". It is a lot common in Voyagers (HP10c, 11C..., 16C).
But you did not mention if the key response to touch fails or not. Is it working fine? No bad or repeating contacts?
Hope this helps.
Success.