T-motor w/ pixhawk doesn't give linear throttle response

I’m currently using a no-name motor on mt 700 quad. I wanted to switch to an upgraded T-Motor MN3520, but when I plug it into a pixhawk or Pixhawk 2, I don’t get a linear throttle response. The motor doesn’t spool up until I hit about 1/4 throttle and when I go to max throttle, the motor only sounds like it’s running half speed. When I connect the motor directly to the ESC, it performs as expected and revs nicely and linearly with throttle.
I’ve calibrated the ESCs, radio and did all of the obvious setup procedures, but can’t get proper performance.
I’ve read a lot of forum posts of people using T-motors and have never seen a mention of this type of issue.
I’m at a total loss on what else to try, but I have these great new motors sitting here and would like to put 'em on.
Thanks in advance for any inputs or thoughts on this topic.

Someone else may have a quicker answer… perhaps if they’ve encountered this before?

I don’t know what’s going on, but I can try to help find out. Could you post a DataFlash log file demonstrating this behavior?

I don’t have the log handy, but I’ll set up my test configuration again and create one.