There's a hardware problem with the cache device resulting in read errors:
Feb 14 17:13:20 Tower kernel: ata8.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
Feb 14 17:13:20 Tower kernel: ata8.00: failed command: READ DMA EXT
Feb 14 17:13:20 Tower kernel: ata8.00: cmd 25/00:20:20:82:35/00:00:1c:00:00/e0 tag 9 dma 16384 in
Feb 14 17:13:20 Tower kernel: res 51/40:00:00:00:00/00:00:00:00:00/e0 Emask 0x9 (media error)
Feb 14 17:13:20 Tower kernel: ata8.00: status: { DRDY ERR }
Feb 14 17:13:20 Tower kernel: ata8.00: error: { UNC }
Feb 14 17:13:20 Tower kernel: ata8.00: configured for UDMA/133
Feb 14 17:13:20 Tower kernel: sd 7:0:1:0: [sdc] tag#85 UNKNOWN(0x2003) Result: hostbyte=0x00 driverbyte=0x08
Feb 14 17:13:20 Tower kernel: sd 7:0:1:0: [sdc] tag#85 Sense Key : 0x3 [current]
Feb 14 17:13:20 Tower kernel: sd 7:0:1:0: [sdc] tag#85 ASC=0x11 ASCQ=0x4
Feb 14 17:13:20 Tower kernel: sd 7:0:1:0: [sdc] tag#85 CDB: opcode=0x28 28 00 1c 35 82 20 00 00 20 00
Feb 14 17:13:20 Tower kernel: print_req_error: I/O error, dev sdc, sector 473268768
Feb 14 17:13:20 Tower kernel: BTRFS error (device sdc1): bdev /dev/sdc1 errs: wr 0, rd 1327, flush 0, corrupt 0, gen 0
This is corrupting the filesystem, they are logged more like an actual SSD problem but try a swapping cables and controller first and see if these go away, if not you'll need to replace it, also will likely need to re-format pool to fix current corruption.