Cymatic has been aware of this problem for some users. In our test scenarios (with multiple Behringer mixers) we were never able to reproduce the problem at 48kHz.
The reason we do not have a solution for this is that we do not know yet if it is a Behringer problem(48kHz clock) or some problem in mixer’s settings or a Cymatic problem. The safe bet until we find a solution is to use 44.1 kHz.
As soon as we get to know more, we will update you.