Adding space to a VM

We are in the new stages of using the IDPA DP4400. We have 3 file servers in a backup job using the file system dataset. When we have to add additional space to these VMs, the backups start failing. I've talked to support and they've recommended turning on the overtime feature, with no success. After pausing these file server backups for a week or so, they eventually complete with success. But when we're forced to add space to the VMs, the backups start failing again. 

Is there a process for the IDPA for this scenario?