Sorry about that. I did upload the files but then the problem went away. However, a short while later (that same day!), when working on the same scene, the problem re-surfaced. I was in the act of updating our ticket, but we have found it is happening more and more in pretty much all of our projects. I believe it is related to using solidrocks, but I can’t be absolutely sure. I have since started using a different method for rendering which is far more manual - using LC and BF, and for the moment, the problems seem to have gone away.
When I have more time, I will try and follow this up, but my gut feeling at the moment is that Solidrocks is doing something weird that freaks out locally rendered buckets.