Hi!
I just want to write some info here with my setup and solution to this problem.
Hardware: ASUS Ryzen 7 7000, ASUS Prime x670-P, 4x Corsair 48 GB HD DDR5, and a Crucial T700 2TB (w/ a heat sink of MOBO) as a system drive for Windows 2022 (21H2 - 20348.1970) server. This drive was connected with a BIOS option of NVME RAID mode enabled as two other NVMe drives were configured within a RAID1 array.
The backup target is inside this same server of a StorageSpaces multitiered mirrored virtual drive (first formatted for ReFS than NTFS) - two SSD and 8 x 2 TB WD HDD, total of 8 TB available space.
First the urBackup server was installed inside this server as a container of a Hyper-V client Ubuntu server and the target of the main storage was shared via and SMB3 share (through internal network). All clients backups were successful except my server above made a BSOD after starting first full image backup. No chance to have some logs as the debug files were empty after a reset switch 
Than I ditched docker setup and switched to direct Windows install on my server OS (see above). While with this setup there was no BSOD but the server hanged and was total unresponsive (service could not be stopped, no remote access was available, only ping worked).
Than I dropped RAID1 from the other two NVMe drives and switched to SATA mode inside BIOS of all NVMe drives (no option to turn this on one-by-one). I managed to switch the boot drive from RAID to SATA without reinstall (see here).
And voila. My backup is currently running flawless with a 3 GB/s speed locally. The main reason probably was with VSS cannot handle the above configuration. THIS IS NOT an UrBACKUP ISSUE! Just for anybody who has hard time with a similar config.
Thank you for reading and for this excellent software.
Regads,
Zsolt