Unraid sends the spin up command before unmount, the main issue appears to be these errors right after the spin up command:
Feb 9 09:18:56 Odin emhttpd: Spinning up all drives...
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdm
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdj
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdg
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdr
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdf
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sds
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdn
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdo
Feb 9 09:18:56 Odin emhttpd: spinning up /dev/sdi
Feb 9 09:19:12 Odin kernel: sd 1:0:16:0: attempting task abort!scmd(0x00000000826327ac), outstanding for 15458 ms & timeout 15000 ms
Feb 9 09:19:12 Odin kernel: sd 1:0:16:0: [sdr] tag#2325 CDB: opcode=0x85 85 06 20 00 00 00 00 00 00 00 00 00 00 40 e3 00
Feb 9 09:19:12 Odin kernel: scsi target1:0:16: handle(0x001a), sas_address(0x5003048001f32ea4), phy(36)
Feb 9 09:19:12 Odin kernel: scsi target1:0:16: enclosure logical id(0x5003048001f32ebf), slot(20)
Feb 9 09:19:12 Odin kernel: scsi target1:0:16: enclosure level(0x0000), connector name( )
Feb 9 09:19:12 Odin kernel: sd 1:0:16:0: device_block, handle(0x001a)
Feb 9 09:19:14 Odin kernel: sd 1:0:16:0: device_unblock and setting to running, handle(0x001a)
Feb 9 09:19:14 Odin kernel: sd 1:0:16:0: [sdr] Synchronizing SCSI cache
Feb 9 09:19:14 Odin kernel: sd 1:0:16:0: [sdr] Synchronize Cache(10) failed: Result: hostbyte=0x01 driverbyte=0x00
Feb 9 09:19:14 Odin rc.diskinfo[9313]: SIGHUP received, forcing refresh of disks info.
Feb 9 09:19:14 Odin kernel: scsi 1:0:16:0: task abort: SUCCESS scmd(0x00000000826327ac)
Feb 9 09:19:14 Odin kernel: sd 1:0:17:0: attempting task abort!scmd(0x000000008c9f9c76), outstanding for 18152 ms & timeout 15000 ms
Feb 9 09:19:14 Odin kernel: sd 1:0:17:0: [sds] tag#2446 CDB: opcode=0x85 85 06 20 00 00 00 00 00 00 00 00 00 00 40 e3 00
Feb 9 09:19:14 Odin kernel: scsi target1:0:17: handle(0x001b), sas_address(0x5003048001f32ea6), phy(38)
Feb 9 09:19:14 Odin kernel: scsi target1:0:17: enclosure logical id(0x5003048001f32ebf), slot(22)
Feb 9 09:19:14 Odin kernel: scsi target1:0:17: enclosure level(0x0000), connector name( )
Feb 9 09:19:14 Odin kernel: mpt3sas_cm0: mpt3sas_transport_port_remove: removed: sas_addr(0x5003048001f32ea4)
Feb 9 09:19:14 Odin kernel: mpt3sas_cm0: removing handle(0x001a), sas_addr(0x5003048001f32ea4)
Feb 9 09:19:14 Odin kernel: mpt3sas_cm0: enclosure logical id(0x5003048001f32ebf), slot(20)
Feb 9 09:19:14 Odin kernel: mpt3sas_cm0: enclosure level(0x0000), connector name( )
Feb 9 09:19:15 Odin kernel: sd 1:0:17:0: device_block, handle(0x001b)
Feb 9 09:19:15 Odin kernel: sd 1:0:17:0: task abort: SUCCESS scmd(0x000000008c9f9c76)
To me this looks more like an LSI or (LSI + those specific drives) issue, can you test with v6.8.3 to see if it doesn't happen?