Probem with BAT preamp & Joule amp component mix

I am having a problem I hope someone can help me figure out and hopefully correct. I am using a BAT 5i pre-amp with Aleph 2 monoblocks or a BAT VK 200 stereo amp with Audio Physic Virgos. With this component mix everything is works fine. I have just received a pair of Joule Electra Heaven’s gate amps, which will eventually replace the Alephs. What is happening is when I turn the digital readout on the BAT 5i pre-amp to zero or engage the mute switch I get a loud pop (more like a loud snap) in the speakers and the Virgo side woofers do a major extension foreword and back. I swapped out the BAT 5i with a BAT VK30 pre-amp with the same results, however when I used a VTL 2.5 pre-amp it works perfectly.
It must be something in the design of the BAT volume control that when the volume is totally cut out, like when its muted or moved to zero, that something is discharging into the speakers. But why only with these amps? And what can be done if anything other than replacing the BAT pre-amp.
Currently my fix is never to move the volume to absolute zero and to never engage the mute, which I do use frequently when listening to LPs.
Your help would be greatly appreciated.