I don't know why, but once I had an issue with a cable where the continuity check was fine, but there was a problem with the cable. The symptom was a channel imbalance.
I discovered that using the Ohm test of the multi-meter detected an issue. I set the Ohm meter (Ω - resistance mode) to automatic and started to probe the hot and ground on the cable. you are looking for a 0 reading as there should be nothing connecting these two wires. If you get anything other then 0, there is an issue.