Cartridge or tonearm problem?

I’m having a strange problem with not getting any high frequency sound out of my right channel. The woofer is moving but no sound out of the tweeter. Left channel is good. I just had a new cartridge mounted and set up by my local dealer a week ago. Everything was sounding great up until I just tried playing records today. I tried crimping the cartridge pins a bit tighter - thought it might be a lose cart lead. Nope. I This was also happening intermittently before getting a new cartridge as well. I talked to a different dealer on the phone before getting the new cart installed. He thought it was due to the stylus not riding evenly in the record groove. I have not messed with the settings at all since having the new cart installed. Very strange that it would play great for a week with a new cartridge but not it’s acting up again.  I dunno. Very frustrated. Any ideas? Thanks.