if you are having power weakness, it could cause some of the relay combos to not 'turn over' and if it skips some steps, the vol could be wrong for a while until that one or two relays finally turn over by chance. that is very common if the psu is borderline in ability to keep 5v.
note, that the 5v line needs a GOOD half amp or even amp to really do its job.
IR sensor should not be affected. if the lcd stays on and does not dim, the lcd1 is getting enough power. but the relay boards may not.
if the ir is not reliable, maybe IR learn was not done with a good signal or maybe the ir remote is low in batts. try to find a sony compat remote with fresh batts and once that works, you can try alternate remotes; but sony protocol is the easiest to lock onto (I can get it from a room away, oftentimes)