Nagra BPS distorting

Just got the Nagra BPS, along with VPI scoutmaster and Benz wood-bodied S M. currently using synergistic interconnects. My preamp is PS audio 4.6, to a tannoy SR840 and Klipsch CF-4...

the nagra distorts, and looking at the signal on a DAW, it's definitely clipped, but the output isn't all that hot, coming into the DAW at -4dB. troubleshooting around, the PS audio phono stage doesn't distort (therefore not the benz) and the nagra has been swapped with another one, same problem. the nagra is loaded properly for MC, and the distortion also occurred with a benz glider, set for MM in the nagra. Tried powering the nagra with new battery, also with 9v DC external. no change.

the same cartridge and nagra worked fine at the store, every time, sounding great even with hot LPs. so, I tried using the nagra straight into the power amp, into some studio gear that has attenuators for hot input, and nothing changes much.

the shop where I bought all this new stuff is without a clue as well. no one at nagra has a solution. I have patience and faith, but at the moment, we're at a standstill.

why does it work well only into their preamps or integrateds?
Cartridge loading (whether it's just right for your cartridge or a litle off) will affect gain very little. However, your Benz has an output of .8mV which is getting up into MM territory. And with the fancy step up transformers in the Nagra, it may be too much gain to be used with the Benz on the MC setting. Try it with the MM input and see if that helps. Also make sure you are using the correct input card for your cartridge's internal impedance (which is 24 ohms, somewhat high for an MC.)
So if it works at the store with the same cartrige and this same nagra bps works at the store, it's likely not the cartridge or phono stage. (assuming you're cartridge at home is performing fine with another phono stage).

Could it be a cable shorting? Anything from the cartridge clips to the phono-pre interconnect. It could also be the particular input your using on your pre amp.

I would not assume it's a issue with your Nagra BPS.