At the moment when using the data locality Scale out policy along with Backup Copy Jobs with Full GFS restore points.
There is no way for the Backup Copy Job to start using a different extent when the extent is becoming full or to just balance them out a bit without first running a manual Active full.
It would be good if when creating the GFS files Veeam could then choose a new extent.
As right now 1 of my extents is getting low on space where as the others are fine. But to fix I need to run a active full which will mean copying all the data to our DR site again.