Creda tumble dryer belt question

[ipbr21054]

I have a creda 37548 tumble dryer.
I opened the door & noticed that even though the drum was full of warm air the drum did not actually spin.
I removed the side to find that the belt had come off & it looked as if i should change it anyway.
I bought a new belt and checked it for size with the old one and fitted it no problem.
Operated the dryer with the door open & the drum spun no problem.
Been using the dryer now for 4 days and the belt has come off again.
I have removed the 2 metal feet with the jockey wheels on and inspected them and all looks ok.
Any advice why the belt has come off or it it just pot luck ????

 

[rocks1]

Is the drum spindle broken ie is the drum loose if not check the pulley is not loose if that's ok refit belt see what happens.

 

[ipbr21054]

drum spindle seems to be ok and no movement.
pulley,do you mean the 2 fitted to the metal brackets which tension the belt ?

There are 2 metal brackets which have a plastic wheel on both which guide the belt,these wheels run on the back of the belt.
I will fit the belt tomorrow and see what happens,did not know if there was common fault.