The 5 speed uses an external slave cylinder with a separate release bearing in the gbox, 6sp uses an internal slave/release bearing.
There is no cable used Ricardo T, only hydraulic.
The crunch is something we've come across, more so on caddy rather than transporters. Although given that you say it does the fault in first, I would be looking in to an issue with the clutch rather than the box itself. Would be surprised if it was covered under warranty (whether VW extended or a non franchise warranty)