I have the same problem... Copying VirtualDisk files (200GB / 50 GB) is also almost impossible within the NAS system... 100% CPU utilization, copying process then aborts. Accessing or copying to an external USB3 SSD (4TB) is also simply not possible; the USB disk is sometimes recognized and sometimes not...
Access after the boot process via HTTP is also a game of chance (BOND network) - ping works, access via HTTP is not possible. SSH sometimes still possible for another rebot. Furthermore, mounting NFS shares on my ProxMox server is not possible, despite the corresponding authorizations I get the message "Access dienied (500)" when trying to mount...
6.0.436 is very unreliable and unstable. It is beta - as you said - but the basic functionality should be given...
-----------------------------------------------------------------------------------------------------------
F4-423 |TOS 6.0436 | 4 x 8 TB HDD | 2 x 1 TB NVME | 32 GB RAM