Ok, if you tried every A841 unit, then it should not be a control board (MM board) issue.

You can see the meanings for LED colors and error codes here https://bitcointalk.org/index.php?topic=3224256

You have tried installing a fresh new OpenWrt firmware.

You have tried different AUC3 5-pin cables.

What are the technical specs for your 5VDC wall wart psu connected to the controller?