Firmware version 126.96.36.199 does not exist in a DAD product, so I assume it refers to an Avid MTRX Studio in which case you should contact Avid for further support.
This behaviour typically happens when the samplerate of the source does not match the samplerate of the box, or when th esource is not synchronised to the box. You can check the samplerate of the source in the routing matrix when you expand it to a channel view. The channel view will the samplerate of the incoming signal to the left (you may have to scroll down a bit). Also make sure there is a green circle next to the source and not a yellow or red triangle.