There is another post in the forum that might be applicable (a long shot maybe): Restore (over 2Tb) gets to 100% then never completes
Is your host server ubuntu with a virtualized windows server 2019 running in a VM? And the windows vm has 3 partitions, an OS disk (physical or a partition?) and 2 5Tb physical drives? Is the 5Tb drive you are trying to restore to in a RAID configuration; virtual or physical? Or a Microsoft storage spaces configuration to expand multiple drives into a 5Tb disk?
When you do the urbackup image backup of the VM, is the urbackup client running INSIDE the vm to perform the image backup? Or is URbackup client running on the host (which I think is unbuntu?) and you are backing up the vm by backing up a large vm disk file?