"Copper grease" isn't a lubricant, it's an anti-seize compound. It has copper flakes in it which will act as solid shear particles if something does stick, usually intended for either steel fasteners, nuts and bolts, or parts fitted into cast iron and not subject to continual movement. The copper can act as an abrasive.
I remember watching a programme about Fred Dibnah doing a tour on his steam traction engine and having a front wheel bush seriously wear. They suggested it was the wrong type of brass used (he got something from a scrap yard for it), but his lad was then shown liberally lathering it with copper grease. It's no surprise it wore out.
Silicone grease is usually recommended for brake caliper sliding pins, I use a type with ptfe added.