I think the E-Flite motors are made well, however I also recently learned of a PREMIUM racing motor maker who showed a 1000 RPM difference among 8 samples of the same top of the world-class motor - so kv happens...!
Check your motor connections for bad solder joints and possibly check for termination issues in the can. The wires could be shorting on the can if the heat shrink has pulled away. The E-Flight motors are nicely built. +/- 5% to 10% on Kv from motor to motor can be expected. That shouldn't however effect the set rpm mode result.
Thanks for all of the input, my problem right now if the lack of day light to try any of these fixes. The florescent lights in my shop and tachs don't mix