Servo motors are not disabling/releasing after setting angle to None

I'm using a Raspberry Pi 4 to control the PCA9685. I have generic MG996R-style servos connected (2 different brands). When I set the servo.angle = None, the servos just hold their current position without releasing.

I'm using servokit 1.3.13, pca9685 3.4.6, and motor 3.4.5

(I do have a version on a different raspberry pi that is running servokit 1.3.6, pca9685 3.39 and motor 3.3.2 that does work correctly, though it uses a different brand of servo).

I am not quite sure if this is due to a regression or certain brands of servos not recognizing the angle = None.

Any insight would be appreciated. I may try to upgrade the second raspberry pi and see if those servos get the issue. That would help narrow down if this is a per-servo-brand bug or a regression.

Start by reproducing angle = None with the reported servokit 1.3.13, pca9685 3.4.6, and motor 3.4.5 versions, then compare it with the working older setup described in the issue. Use the servo angle-setting entry point and the version comparison to determine whether this is a regression or servo compatibility issue; done means the cause and expected release behavior are established.

Written by the indexing model from the issue text.