Attenuator volume drop problem

[GLFSHNT]

I have a Rivera Rock Crusher attenuator.  It works well.
My problem I think is with an amp

I built a tweed deluxe 5e3   it works well and sounds great.

When using the attenuator on the "studio" (quietest) setting with Amp volume 4 or higher
and guitar on 10.... When I play a hard chord  the amp volume will drop to nothing quickly, I stop for a second and it comes back.  If I turn down the guitar and play really soft it's OK.
Seems like once you start driving the amp it shuts down.

Only mods - I swapped the 12AX& for a 12AY7 and changed the 2 caps to clean up the low end. 

Amps seams to work fine on other attenuator settings and without it.
I really want to studio setting to work.

I am fairly new to the world of building amps and looking for any input here.
Thanks

[shooter]

the amp volume will drop to nothing quickly

normally I would think you're swamping the coupling caps feeding the PI, but your description leaves me guessing your attenuators impedance is wacked

[92Volts]

Have you ever played it fully cranked into the other attenuator settings? If it works when being played the same way into another setting, it pretty much has to be an attenuator problem.

Rivera website says this attenuator can go down to "silent"... when you're using it on the Studio setting, do you still have a speaker hooked up? Are you listening to it through the speaker or through the Line Out with headphones or through a computer? If you're using a listening device other than a speaker, does that device work on other settings?