Hot Rod Deluxe III tone stack issue.

[jvm]

Hey guys. I have a HR Deluxe III on the bench. Everything works normally except when treble pot is wide open. Then it sounds as if I am shorting the input with my finger. Customer says that V2 has been replaced due to failure caused by this issue. Any ideas?

[pdf64]

It does this even with the OD channel gain or clean channel vol turned down?
What happens to the tone / waveform when it's doing this thing?

[jvm]

Found the problem. Bad V1 12AX7. Thanks for trying to help, pdf64.