I had a tube going bad lost vacuum and started having a intermittent muffled Left channel and so I threw a Svetlana 6as7 Coke bottle tube in it now the Left channel is constantly muffled I've done a sloppy EQ job and it sounds close to the right channel now.
I would throw some cheap headphones and poke around the amp while it's playing with a wooden chopstick to see if you can change what you're hearing by poking at various parts. I suspect you have a flaky solder joint that's acting up somewhere causing something close to a signal dropout.
Sorry for being so slow I've been procrastinating I poked around for a while and it stayed the same no clunks no clicks no change although the more I use it the better it gets maybe it's the new tube idk