They should just pull out, but careful they can be fragile. Don't make the mistake of yanking on it if the cable is the soldered through ones with plastic support, you can tell by checking the thickness of the pins on the other side of the pcb.
Isolate the problem 100% to the amp. Inspect everything on the PCB first, write down voltage and signal levels and refer to the service manual/schematic. Compare to what you get when the fault is occurring. Perform intermittent fault type testing such as tap testing, heat testing, cold/warm/fully depowered state testing, clean the connectors, then if no joy start on checking all the surface mount caps especially if it's a few years old.
Google it as well, these type of problems may be common to the model.