this test you can swap if out with the diagonally positioned motor and working ESC assembly
to see if it will function with another set in this position.
If this does not isolate the issue then this would determine that the main flight board is the
problem meaning it will need replaced. Not very expensive, all things considered, but a long,
tedious and involved process.
Note:
Be careful if you need to order a replacement esc or motor (so far there seem to be two
distinct versions of the esc and motor) as they should all match ratings and values otherwise
there can be balancing and other issues when you install a new but unmatched one.
