Mar 26 12:00:21 statiknas kernel: ata9: EH complete
Mar 26 12:00:21 statiknas kernel: ata9.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
Mar 26 12:00:21 statiknas kernel: ata9.00: irq_stat 0x40000000
Mar 26 12:00:21 statiknas kernel: ata9.00: failed command: READ DMA EXT
Mar 26 12:00:21 statiknas kernel: ata9.00: cmd 25/00:08:00:2a:81/00:00:a3:03:00/e0 tag 8 dma 4096 in
Mar 26 12:00:21 statiknas kernel: res 53/04:08:00:2a:81/00:00:a3:03:00/e0 Emask 0x1 (device error)
Mar 26 12:00:21 statiknas kernel: ata9.00: status: { DRDY SENSE ERR }
Your issue is cabling. SATA connections are terrible, and depending upon the type of drives, the non-locking cables are better than the locking ones (eg: on WD drives)
Reseat the cabling at both ends, along with the power, avoid splitters at all costs, and do not try and make cable runs look pretty -> the prettier it is the more susceptible to cross talk it is and never, never, never tie power cables to data cables.
When doing this, take care not to disturb any adjacent cables. Whenever I'm in my system I always give a little push to every single sata cable everywhere.