It's not just ata14, it's ata14.00 to ata14.04, the five disks on the port multiplier, SATA port multipliers are not recommended, though unlikely it's causing the sync errors, but if nothing else it will be causing performance issues.
Also because of the log spam caused by that there's nothing else to see, can't even see if it was a correcting check, first step would be to run a correcting check and then a non correcting one to see if the errors keep happening, ideally after getting rid of the port multiplier.