The gray section of the coax can be run together, it is the exposed center that is the antenna and should be separated and at 90.

If it was me I would move the ends away from the servos, they are brushed servos if I am not mistaken.
The brushes if worn may cause excessive sparking under load which may cause RF noise. Random RF noise that close could swamp out the real signal resulting in failsafe, then the servo motors stop moving, the RF noise goes away, signal is now good, regain control. I am not saying this is the problem, just something I would change.
Need more info and debug-testing.