I recently bought a set of Sherwood engraved brass cups with 3 load balls. 2 of the load balls seem to be very tight and get slightly stuck in the cups.

Does anyone have or has had the same problem? I've got a smooth copper set with 4 other load balls and they are all a perfect fit. It's a bit of a downer at the moment.

Have you tried those 4 perfect load balls from the copper set with the brass cups? If those 4 perfect load balls get stuck in the brass cups also, then it must be the brass cups that are too small. If they don't get stuck, then it must be those two new load balls you purchased with the cups that are too big. Either way, you should be able to find the culprit and go from there.