I am also building a 2.6 and have been down a very similar path as you; erratic thruster behavior somewhat remedied by unplugging the camera servo. With only the ESC's plugged in (D6,D7,D8) , I have fully operational STBD and VERT thrusters, but PORT only twitches and chatters and will not turn a full revolution. I can program PORT, but am unable to calibrate it.
Fearing a shorted or broken wire, I installed a brand new PORT thruster. But even the new PORT motor still chatters.
All ECS's are programmable, but behave somewhat differently:
-VERT ESC tones (when programming) and LED's light appropriately - thruster works fine
-STBD ESC does not tone, lights appropriately - thruster works fine
-PORT ESC does not tone, lights appropriately - thruster chatters
(If I didn't know any better, I'd say the tone actually comes from the thruster motor, not the ESC?)
The only other PORT ESC symptom is that occasionally the red LED freezes 'on' after issuing keyboard commands. The only remedy is to power cycle the entire system.
Additional ESC troubleshooting :
I removed the PORT ESC, leaving only the STBD and VERT installed on the board:
PORT ESC removed
STBD ESC installed
VERT ESC installed
This configuration resulted in the PORT AND STBD thrusters chattering?! Vert thruster worked fine. With only two ESC's installed, three thrusters were affected?
After reinstalling the PORT ESC, VERT thruster sill worked fine, STBD worked fine, and PORT went back to the only thruster chattering.
I reheated all ESC connections just to make sure there were no cold or shorted joints.
I also checked to make sure that there were no shorts in the DB25 connector.
As for now:
I remain stuck with two out of three operational thrusters, and have still yet to plug the camera servo back in.
Charles - would you mind sharing what you learn with the new ESC?
Any further community input would be most appreciated!