Latching switch types ok for VCRs etc, with tight clearances but not here. 2 DPDT worn , leading to snap crackle and pop etc unless you hold the knob in or out. There is about 2mm of play between the knobs and the holes in the metal of the front/rear panels. Replace those 2 plus 2 more with same flimsey 0.1 inch pin spacing switches and try and find or make larger knobs ? Replace with heavier duty switches, larger footprint , requiring re-positioning/drilling/wiring-in ? The 2 off 4PDT switches maybe more resilient to off axis loading so will leave as is , unless anyone knows better.
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on