Wow. I've never heard of connectors being so difficult to get on. Were they Eichmanns?

Be careful when you remove them, I remember we sold a brand of ICs (Distech, I believe) that fit so snugly, some people ripped the metal sheathing off the RCA inputs when they pulled them off their components. Not an issue if the RCA inputs are solid metal (like Tiffancy, etc.) but if the are metal-sheathed plastic, try rocking them a bit before pulling back.