RE: Need opinions on what could be wrong
I don't know this particular ESC, but I do believe that auto LVC simply detects your cell count automatically, and will not have any impact on cutoff treshold.
Can you post a sketch of your wiring harness?
If you got your wiring put up in such a way so that the two ESCs can work as a voltage divider for each other, then the LVC will trigger once you get just a slight differential load on the motors.
Do you have a wattmeter? It would be very helpful, to get some recordings on max amp draw and minimum battery voltage under load.
The fact that both ESCs is doing the same thing might indicate that the ESCs are not at fault, and the problem lies within the configuration. Either of the ESCs them self, or some other part of the drivetrain.