Not sure what speed control AVID uses, but most speed controls have a small voltage drop at max voltage, but it's usually a little over 9V.
Most VFD's have settings to compensate, but the HY does not.
Hopefully AVID has a solution.
What I did (using UCCNC) was to set the max PWM in the software to 50% and set the Huanyang to 0-5V, and it worked well.