Are you sure there's a motor in those door actuators? Not a simple electromagnet?
Most modern door actuators are motors, you can hear them work! This one obviously has a motor unit and a
rack-and-pinion section from the shape.
They are certainly not rated for continuous use, nor for use under continuous stall (I suspect the circuit driving them senses stall and cuts the power automatically - modern motor control is smart)
Basically any electric motor encased in plastic is likely not for continuous use, motors need ventilation or metal heatsinking to work continuous due to the high power densities involved.
I'd be tempted to see if the plastic casing can be partially removed to help cool the motor part.