Fusion FA123 - Protection Shutdown

Evening all,

I have just finished installing fusion fa123 amps to my 3 way speakers and dialled in basic crossovers. However, the left channel (slave amp) keeps going in to protection mode. The flashing light indicates a high temp. After I have switched them both off for a while and they have cooled down I find that the slave amp has reset the input setting to Auto and the volume to -96db. However, after switching the input back to SP/DIF and adjusting the volume the best I can achieve is a broken signal.

Any ideas?