I`ve got one on a double door Paul

Tried to adjust it as was not quite closing flush - Fxxxxd it up good & proper & took 1 1/2 hours to get it working again including full strip down so now understand how they work

then found out one of the springs had twisted & was catching on the bracket
took 10 secs to fix & tighted a lock nut

Will find the make for you if you need as is quite a good one - even allows you to phone it to open

the door itself is fiberglass (althought you couldnt tell from the outside), presumably for weight
If you have an ally one it might need changing