Pick up another "Brick" and pitch the one you have
Aw, come on now, where's your scientific curiosity?
We might be on the verge of discovering a time related degradation in this entire class of cameras! And it's possible it could be fixed by a tiny dab of black goo. I've had mine for nearly fifty years, since new. If it was acting up, I'd want to try fixing it.
(Truth be told, if my C3 expired I would let it be a
sleeping brick, as I have three Canon SLR bodies and an assortment of FD lenses for my 35mm needs.)
DaveT