I am guessing on the brake design, based on my experience with linear actuators we use and build here. It’s possible the lead screw angle will prevent backdrive. My experience is with actuators handling 1000+lbs load, and they will definitely reverse in the event of brake failure. The motor resistance and lead angle are not sufficient to hold the loads.
I know we are talking about a lower loads here, and it may be insufficient to reverse in the event of failure, but it is a possibility.