You have a null device:
Dec 13 13:48:13 Unraid unassigned.devices: Disk with serial '', mountpoint '' is not set to auto mount and will not be mounted...
It looks like it might be your TREKSTOR device:
smartctl 7.0 2018-12-30 r4883 [x86_64-linux-4.19.88-Unraid] (local build)
Copyright (C) 2002-18, Bruce Allen, Christian Franke, www.smartmontools.org
/dev/sda: Unknown USB bridge [0x1e68:0x1087 (0x100)]
Please specify device type with the -d option.
Use smartctl -h to get a usage summary
I'll make a change so the php error won't show, but this device won't mount.