Technics sa-203 left channel issues

Have a technics receiver from the 80s and ocassionally like once every few months or so the left channel crackles in and out only at low volume. Balance and volume are digital 3 band eq is analog but when acting up moving the eq doesnt solve it. I keep checking rca and speaker cables and everything seems ok. Bump the volume up and it goes away. Anyone seen issue like this. I think tomorrow ill switch the rca cables from tv to video input and swap speakers and wait until I notice issue again and see what happens. Im not a hundred percent sure that the signal isnt coming degraded from the directtv box itself as ive noticed lower volume but not crackling on same channel in another room but volume adjustments dont affect it. Just depends on channel. This time it happened tonight as soon as I bumped it to tuner it went away but tuner is louder as soon as I switched back to video the signal was fine.

Anyones thoughts. failing speaker? Bad cap in amp? Shitty rca cables? (they were a high dollar thick plated set but are several years old maybe 10 appear to have no damage though). Speakers are bose 201 series II or III not sure

Doesnt follow speakers. Popped back on when I bumped the wires on the back of the amp so I redid speaker connections and pulled rca cables and reinstalled. Now hoping its gone or atleast a bad set of cables. I love this amp and really dont want another recap on my hands being so busy these days

Random crackling noises in an amp of that age points me to a transistor, specially differential pair transistors. You can isolate the bad one with a freeze spray, or replace them ( probably the transistors are cheaper than the freeze spray to test them...)

speakers relay can do some noises too...

Ill keep that in mind. Thanks so far so good just have to see if it resurfaces in a few months or stays away