Garage roller door motor not stopping when closed

Question

I just replaced two broken straps on my roller garage door. They look like below (when not broken).

Everything went well (tested with manual crank up and down etc..) but then I closed the door fully via the motor. It did not detect that it had reached the bottom and the motor carried on going. I wasn't quick enough in stopping it and the straps were smashed to pieces. Lo and behold - exactly as per the original damage. So now I know why they were broken!

As the straps only cost me £20, I'm inclined to have another go at this, as long as I'm better prepared for the closing problem.

So here's the question: Why did the motor not stop? Do I need to do something to reset the system to the fully closed position? Does it sound like an electrical fault, or did I just miss a step?

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The door is pretty old. Installed by previous home owner about 10 years ago. I don't know the manufacturer or model. The sticker on the unit is for a distributer/fitter. I rang them and they were not helpful. All I know is it's a pretty basic insulated roller door with 55mm slats. It has a simple remote control and obstruction detection for the motor.

Answer 1

I bought a new pair of straps and had another go...

Although I couldn't find any manufacturer's instructions for the door or motor, I did find some instructions for the remote control unit which mentions doors having screw limit switch adjusters. On my roller they look like the photo below.

With the door half open I decreased the travel for both up and down directions and slowly incremented them until the door stopped exactly at the top and exactly at the bottom.

I'm still scared to open and close my door without my finger hovering over the stop button, but so far it works and has saved me quite a bit of money.