771 and 775 codes on only one receiver

I have two HR24-500 receivers and one HR44-700 genie in a whole home system. I get CONSTANT 771 and occasional 775 error codes on only ONE of the HR24-500 receivers. Often, disconnecting the coax cable from the back of the receiver will solve the problem. Sometimes it will require multiple disconnects to resolve. For a couple months, I even switched the coax cable between the swim splitter and the receiver, but still got the codes, so I switched back to the original coax cable, which leaves me to believe that it's not the coax cable. I have unplugged the swim box without it solving the problem. It seems streaky, as it went for a while without the problem, and recently we have had a lot of rain for several months along with more error codes during the same period. If it is a connection problem between the dish and the swim box, why would disconnecting the cable from the back of the receiver resolve the problem at least temporarily? Sometimes doing a red button reset on the box or doing a "clearmybox" reset would solve the problem, but then it would return eventually. This does not EVER happen to either of the other two receivers.