It's one of those things that comes up regularly on the Renault Forums.
The brakes are self adjusting, but because they don't move a lot in service, they seize up, and then you have issues with getting at the calipers and pads.
When we had a Renault Master van, we didn't have that much trouble, but we were on the road every day and it did over 250k miles before we sold it.
Here it is in Quartiera, Portugal:
I'd suggest that if it is seized, then try and find an indy that handles these vehicles, I know we never had the tools to get the front discs off as they were inboard of the hubs, so a major strip down job.