Berlingo Sliding Door Problem!!

[blingo74]

Hi. I've got a 2001 Berlingo Multispace. The problem I have is the driver's side sliding passenger door won't close properly or stay put when opened. I can get it to lock, in the open position by lifting it, then the catch grabs. I'm guessing this is clearly a problem with the runners and/or carriages. What I'm wondering is: Is this a common fault? Is there any scope for adjustment, tightening, quick fixes etc... Which carriage/runner, of the 3 attaching the door to the car, is most likely to be at fault and need replacing etc... I would also appreciate more info on part names, numbers etc... and if possible any diagrams. I'm having loads of trouble actually just finding the parts and any info on the net!!

Thanks in advance for any help...

Blingo!!