Backup failing with error "The transaction does not exist to call rollback on"
The reason for this error is unclear at this time.
Possible workarounds for this include
1) vMotion affected VM to different ESX host. Normaly a simple vMotion will fix this issue but may need to be storage vMotioned.
2) Un-register and re-rgister VM
3) Clone VM
4)Creating new Vm and attaching disks to new vm