Thanks for the responses. I've had the TIU for several years. It is version 'I' and was returned for a factory upgrade. MTH suffixed a silver dot to the 'I' verifying the upgrade. It has always worked flawlessly and yes, I do power it through the aux port.
When I power up Fixed 1-in, my voltmeter shows nothing coming out of Fixed 1-out (dead channel?). I opened the case removed the fuse and it is fine. I switched fuses around between 1 and 2 to see the result. Same thing as before, power up Fixed 1 and no power coming out. Power up Fixed 2 and power out is fine.