cluster mode : major pb in stack list ?

Hi guys
 
I've noticed a major pb when stacking projects in cluster mode on A/V
merging. When running more than one "batched" clustered projects, only first
part on AV psu is OK. All video tracks are OK, but dvdrip does not sync the
rest of the compressed audio tracks except the first branch. This does not
occure when running one single clustered project. 
 
For info, i'm running 5 x X86_64 clones on a 1 Go/b network with NFS shares.
 
regards
 
Pierre