Mark, Dave,
I may have some trouble checking the clocks, I don't own an oscilloscope (I have been looking for one at hamfests) and I don't know of anyone locally that has one.
I have wiggled the cabling and swapped cables etc from one raduino to the other.? It only acts up when I swap in the raduino that came with the unit.? I've tried rocking the raduino a bit as well and no difference.? All the traces seem to be ok on the board, so I'm guessing its either the si5351 or the crystal.? I don't have any way to test either of them that I know of.
73
Spencer
VA3SPN