I have a fireface 400 and octamic II connected via adat. I register multitrack drums using a new 27-inch imac. All audio interface drivers are updated to the latest versions downloaded from the rme site. The card is powered by an original external power supply.
I have a serious problem that I hope to be able to solve: usually everything works fine but at times and randomly the recordings of 1 track (I use 10 microphones) are lowered by about 6/7 db and after a few minutes everything returns to normal. The problem is not microphones because they are new and I have them checked.

I did so many tests by changing cables, pre, microphones. I came to the conclusion that the problem could be the sound card I have been using for 15 years without problems.

Do you have any advice or suggestions to identify this problem and solve it? Have you encountered other cases like mine in the fireface 400? Thanks for the support, I'm very frustrated because I can't work because of this instability.