Troubleshooting Xantrex C60 Charge Controller Suddenly Operating in Diversion Mode?

I am stumped. I have used Trace/Xantrex/Schneider C Series controllers for going on two decades. I currently have 3 seperate 12v battery systems set up on my farm- two of which use 2 C60 charge controllers.

On one of the systems one of the controllers is suddenly giving me a slow orange/red blink. It has been working fine for a couple of years.

I am using a remote Trace meter (set a few feet away) - and on it it says the red flash is Load Control mode. When I disconnect the meter and re-install the light diode (and yes- I made sure the flat side was towards the left- the nearest casing) - it also flashes red - which says low voltage disconnect. (I may have these two reversed- it's been a long day). I've also connected the meter to the other charge controller in the system- and it flashes green (or solid green depending on state of charge) as it should. 

The other charge controller in the system works fine. Battery voltage has generally been 13.5 or so when this has been happening.

I've checked, and double and triple checked the wiring- no appaent problem. Checked the jumpers- all good. No obvious signs of corrosion, no obvious burned parts on the board. "Normal" (slight) amount of webbing, bug debris when initially checked- all cleaned up now. 

This happens regardless of whether the breakers for the solar panels going to this charger are on or not. (When on in full sun with already full batteries they start bubbling- the controller is definitely not doing its job).

Unless I'm missing something the positives from the panels should be isolated when their breakers are tripped. I removed the grounds from the common bar one by one to see if there was possibly a problem there- didn't change a thing.)

LAst thing I can think to add- I'm not sureif the reset button on the side of the controller is working or not. Doesen't seem to do anything with a single push nor throw it to equalization mode holding it for 10...or 30 sconds. 

Any thoughts how to proceed? Did I simply just get unlucky and have one of these fail? Or is there something I've overlooked?