VSB door, faulty

Hello

I just got home to find the metal door on my VSB (auto door) down.
The cord has snapped, it only lasted a month. I cant get hold of suppliers and am concerned about why this has happened, it was fitted as per instructions.
Has anyone else had problems like this?
Thankfully there mustn't have been a chicken entering/exiting at the time as they all still have there heads.

Thanks Jo

You are right it does say that.
We've had a thorough inspection and cant find any reason that it would have snapped.
There was enough on the coil for us to re-tie, but will be keeping a close eye on it in future.
The door was supplied with VSB, the recommended lighter weight I think aluminum.
Joking aside I'm sure it would cause a lot of damage if a bird was unlucky enough to be under it.
I will ring the suppliers tomorrow, if I get any useful response about why it might have happened I will feedback.
Jo