Like Jesse mentioned…..I had a similar problem with a Carver TFM-35. The RCA connector ground solder connection broke free from the board. The RCA connector was a block assembly, like these. Might be worth a look inside to see. Of course power off, unplug and remember caps can hold a charge and they can shock you should you touch the wrong things inside the open chassis.
What folks have mentioned, it’s not clear from your post if you are hot connecting or just twisting connectors after you power on. Hot connecting is a bad idea with an RCA connector as the hot center pin connects before the ground barrel connection does.
Just a little history info, the Lemo Camac connector, like Mark Levinson and others used on their gear, connected ground before hot. That connector didn’t catch on so to speak, the RCA dominated. I still wouldn’t hot-plug components with any type connector.
RCA to Camac adapters.