Motor stutter. Diagnostics. Sunnysky 2212. 20a blheli esc. Navio2.05:31

Having problems with low throttle motor stutter. Thought it was esc’s. Now testing using receiver channel 3 output to individual esc’s (direct connection to transceiver throttle) and all motors show some stutter as minimum throttle. The original front two motors that had the problem have a very slightly higher threshold.