The microphone input level on my tentacle seems to fade.

I’m just testing it through a mixer as generally don’t use the on board mic function as I tend to work on cameras with their own sound inputs, but I’ve got a shoot on a Dslr so thought I’d test it out but don’t have a functioning DSLR

I plug up the tentacle to the mixer with a 3.5mm to twin xlr cable.  Starts off perfectly, audio on one track and screaching time code on the other then after 15 seconds the audio level drops away to what would be an unusable level.  This happens on 2 different units.  Am I missing something?

Thanjs in advance

Chris Bruce