Kenwood KA 8100 Integrated Amp...No sound in left channel ?

I turned on the Amp and had no sound from left channel....and then I pressed high hz filter button. and out several times...the channel came back and it is now playing fine.
Does this indicate a problem ...or just a dirty contact ?
thank you
Dirty contacts. I sold Kenwood in the 70’s into the early 80’s and many came into our service department with noisy controls.
It’s at that age where one possibility, the ugliest of all.. is the one I made with the last three integrated amps I worked on.

Complete switch disassembly (of all switches), and scrubbing of the contacts with 2000 grit sandpaper, reassemble switches, re solder, and then reassemble the gear. They might never suffer a fault in the entire life of the gear, ever again.

That’s the only ’real’ solution that works. Contact cleaner works for a bit, but then......
Contact cleaner like DeOxit works well and works fast. Got my 80's receiver running like new. But, that was only 8 months ago so I cannot comment on the duration of that solution. As teo-audio mentions it might not be a long term solution but could serve as a cheap(ish) (a tiny can of DeOxit is $20...and doesn't spray well either !) stop gap solution.

I don't have the soldering skills to do the permanent job he mentioned or the money (my receiver isn't worth it) to get someone else to do it.