If one of the three headphone wires has a loose contact - I guess it's ground - it is possible, that the mono portion of the signal - which is the same between left and right side - is cancelled out and just the wet portion, which is different on left and right side, survives. We had that scenario once. Just a defective headphone cable.
If you are monitoring via balanced XLR cables, and the cable on one side has its hot wires crossed, and you mix both in a mixing desk, you could have a similar cancellation effect.
Both issues outside of the PROFILER.