Backup failed with error 1859

Hi,

since 2 Days my Backup failed 

i get the Error

Error: 1859 - [rofs_cant_write_detail] RDA can't write //vRanger_423261c9-3f10-7d91-3c8f-8a1dae2c2d64/vRanger_20210510_093916_44b4de82-3e41-4984-ac6c-64fa904c1e0a/.b88adee5-33ec-4bfe-8e28-736dc4a38961/.b88adee5-33ec-4bfe-8e28-736dc4a38961.var (Service is down)

backupdrive is an QUEST DR4100 with RDA

[2021-05-10 09:39:16.130]: vRanger Backup & Replication - v7.8.2.0
[2021-05-10 09:39:16.145]: Selected Options: Update notes with the latest backup results. | Enable guest quiescing. | Enable Active Block Mapping™ (ABM). | Enable Cataloging. | Enable Change Block Tracking (CBT). | Selected SpaceSavingTech: Incremental.
[2021-05-10 09:39:16.145]: Task for virtual machine vRanger was queued.
[2021-05-10 09:39:16.635]: SourceVm:vRanger | Uuid:423261c9-3f10-7d91-3c8f-8a1dae2c2d64 | VC:vcenter.xxxx.local, Host:xxxx.local [ESXi 6.7.0]
[2021-05-10 09:39:16.635]: Beginning backup task for 'vRanger' sichern-vRanger
[2021-05-10 09:39:16.650]: Starting task validation.
[2021-05-10 09:39:16.650]: Connection to vcenter.xxxx.local was properly validated.
[2021-05-10 09:39:16.650]: esxi01.xxxx.local is properly licensed.
[2021-05-10 09:39:16.667]: Test connection to repository vRanger starting...
[2021-05-10 09:39:17.366]: Test connection to repository vRanger successful!
[2021-05-10 09:39:17.366]: Ending task validation... success!
[2021-05-10 09:39:17.366]: Beginning initialization of backup information.
[2021-05-10 09:39:17.476]: Retrieving the tasks parent information.
[2021-05-10 09:39:17.476]: Retrieving save points for any full backups associated with this job.
[2021-05-10 09:39:17.998]: The following options were changed since the last recurrence: Repository.  A full backup will be performed.
[2021-05-10 09:39:17.998]: Finished initialization of backup information successfully.
[2021-05-10 09:39:17.998]: Initialization was sucessful. Backup type to run: Full
[2021-05-10 09:39:22.076]: Retrieving the VM BIOS configuration completed.
[2021-05-10 09:39:55.582]: Creating a quiesced snapshot for vRanger completed.
[2021-05-10 09:40:04.228]: Loading virtual machine 'vRanger' information completed.
[2021-05-10 09:40:07.751]: Local machine is a VMware virtual machine.
[2021-05-10 09:40:07.767]: Skipping VDDK HotAdd.  VMware does not support using HotAdd of the proxy.
[2021-05-10 09:40:07.783]: Check the manual for compatibility issues when attempting Lan-free operations.
[2021-05-10 09:40:07.783]: Backup task will be attempted using a Machine-based VDDK network connection.
[2021-05-10 09:40:11.110]: Filtering out content of pagefile for disk: [Hybrid-VM1] W2K12_R2/W2K12_R2-000002.vmdk
[2021-05-10 09:40:11.600]: Using filter type(s) change block and active map for disk: vix:1:r:vcenter.xxxx.local\:443:0:[Hybrid-VM1] W2K12_R2/W2K12_R2-000002.vmdk
[2021-05-10 10:04:16.729]: Backing up disk 'vix:1:r:vcenter.xxxx.local\:443:0:[Hybrid-VM1] W2K12_R2/W2K12_R2-000002.vmdk:moref=vm-101:snapshot-102528:6' completed.
[2021-05-10 10:04:16.745]: Backup failed: Error: 1859 - [rofs_cant_write_detail] RDA can't write //vRanger_423261c9-3f10-7d91-3c8f-8a1dae2c2d64/vRanger_20210510_093916_44b4de82-3e41-4984-ac6c-64fa904c1e0a/.baafbafc-5a30-444d-bf6f-f6b1ac981e73/.baafbafc-5a30-444d-bf6f-f6b1ac981e73.var (Service is down)
[2021-05-10 10:04:16.745]: The failed backup task will be retried.
[2021-05-10 10:28:22.207]: Backing up disk 'vix:1:r:vcenter.xxxx.local\:443:0:[Hybrid-VM1] W2K12_R2/W2K12_R2-000002.vmdk:moref=vm-101:snapshot-102528:6' completed.
[2021-05-10 10:28:22.207]: Backup failed: Error: 1859 - [rofs_cant_write_detail] RDA can't write //vRanger_423261c9-3f10-7d91-3c8f-8a1dae2c2d64/vRanger_20210510_093916_44b4de82-3e41-4984-ac6c-64fa904c1e0a/.a4416ac8-f546-46c6-93b6-9b071553283f/.a4416ac8-f546-46c6-93b6-9b071553283f.var (Service is down)
[2021-05-10 10:28:22.207]: The failed backup task will be retried.
[2021-05-10 10:52:27.706]: Backing up disk 'vix:1:r:vcenter.xxxx.local\:443:0:[Hybrid-VM1] W2K12_R2/W2K12_R2-000002.vmdk:moref=vm-101:snapshot-102528:6' completed.
[2021-05-10 10:52:28.180]: Updating notes for vRanger completed.
[2021-05-10 10:52:28.180]: Updating VM notes completed.
[2021-05-10 10:52:28.275]: Setting VM event completed.
[2021-05-10 10:52:34.909]: Removing snapshot for vRanger completed.
[2021-05-10 10:52:35.573]: Error: 1859 - [rofs_cant_write_detail] RDA can't write //vRanger_423261c9-3f10-7d91-3c8f-8a1dae2c2d64/vRanger_20210510_093916_44b4de82-3e41-4984-ac6c-64fa904c1e0a/.b88adee5-33ec-4bfe-8e28-736dc4a38961/.b88adee5-33ec-4bfe-8e28-736dc4a38961.var (Service is down)