Uncorrectable parity/CRC error on Seagate ST500DM002-1BD142 KC45

A harddrive as identified below, reported uncorrectable parity/CRC error on two separate occasions this month.

ada1 at ahcich1 bus 0 scbus1 target 0 lun 0
ada1: <ST500DM002-1BD142 KC45> ATA-8 SATA 3.x device
ada1: Serial Number [withheld]
ada1: 600.000MB/s transfers (SATA 3.x, UDMA6, PIO 8192bytes)
ada1: Command Queueing enabled
ada1: 476940MB (976773168 512 byte sectors: 16H 63S/T 16383C)
ada1: quirks=0x1<4K>
ada1: Previously was known as ad6

These are the log messages for the first occasion:

May  7 15:58:10 <kern.crit> enterprise kernel: [446896] (ada1:ahcich1:0:0:0): WRITE_FPDMA_QUEUED. ACB: 61 58 f0 4f 85 40 1d 00 00 00 00 00
May  7 15:58:10 <kern.crit> enterprise kernel: [446896] (ada1:ahcich1:0:0:0): CAM status: Uncorrectable parity/CRC error
May  7 15:58:10 <kern.crit> enterprise kernel: [446896] (ada1:ahcich1:0:0:0): Retrying command

These are the log messages for the second occasion:

May 13 12:48:01 <kern.crit> enterprise kernel: [953887] (ada1:ahcich1:0:0:0): WRITE_FPDMA_QUEUED. ACB: 61 00 50 2e 01 40 07 00 00 01 00 00
May 13 12:48:01 <kern.crit> enterprise kernel: [953887] (ada1:ahcich1:0:0:0): CAM status: Uncorrectable parity/CRC error
May 13 12:48:01 <kern.crit> enterprise kernel: [953887] (ada1:ahcich1:0:0:0): Retrying command

ZFS ran a scrub on Sun May 18 04:46:20 2014, and found nothing to be ashamed of:

  pool: enterprise_zroot
 state: ONLINE
  scan: scrub repaired 0 in 1h7m with 0 errors on Sun May 18 04:46:20 2014
config:

        NAME              STATE     READ WRITE CKSUM
        enterprise_zroot  ONLINE       0     0     0
                mirror-0  ONLINE       0     0     0
                  ada0p3  ONLINE       0     0     0
                  ada1p3  ONLINE       0     0     0

errors: No known data errors

smartctl reports a total of 4 CRC errors, but otherwise the drive’s sound.

smartctl 6.2 2014-02-18 r3874 [FreeBSD 9.3-PRERELEASE amd64] (local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Seagate Barracuda 7200.14 (AF)
Device Model:     ST500DM002-1BD142
Serial Number:    [withheld]
LU WWN Device Id: 5 000c50 03f5711f2
Firmware Version: KC45
User Capacity:    500.107.862.016 bytes [500 GB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    7200 rpm
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA8-ACS T13/1699-D revision 4
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Mon May 19 14:28:04 2014 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x82) Offline data collection activity
                                        was completed without error.
                                        Auto Offline Data Collection: Enabled.
Self-test execution status:      (   0) The previous self-test routine completed
                                        without error or no self-test has ever
                                        been run.
Total time to complete Offline
data collection:                (  600) seconds.
Offline data collection
capabilities:                    (0x7b) SMART execute Offline immediate.
                                        Auto Offline data collection on/off support.
                                        Suspend Offline collection upon new
                                        command.
                                        Offline surface scan supported.
                                        Self-test supported.
                                        Conveyance Self-test supported.
                                        Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                                        power-saving mode.
                                        Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                                        General Purpose Logging supported.
Short self-test routine
recommended polling time:        (   1) minutes.
Extended self-test routine
recommended polling time:        (  83) minutes.
Conveyance self-test routine
recommended polling time:        (   2) minutes.
SCT capabilities:              (0x303f) SCT Status supported.
                                        SCT Error Recovery Control supported.
                                        SCT Feature Control supported.
                                        SCT Data Table supported.

SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   104   099   006    Pre-fail  Always       -       6566432
  3 Spin_Up_Time            0x0003   100   100   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   100   100   020    Old_age   Always       -       43
  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000f   086   060   030    Pre-fail  Always       -       405702078
  9 Power_On_Hours          0x0032   077   077   000    Old_age   Always       -       20614
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   020    Old_age   Always       -       43
183 Runtime_Bad_Block       0x0032   100   100   000    Old_age   Always       -       0
184 End-to-End_Error        0x0032   100   100   099    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
188 Command_Timeout         0x0032   100   099   000    Old_age   Always       -       0 0 2
189 High_Fly_Writes         0x003a   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0022   069   053   045    Old_age   Always       -       31 (Min/Max 31/31)
194 Temperature_Celsius     0x0022   031   047   000    Old_age   Always       -       31 (0 19 0 0 0)
195 Hardware_ECC_Recovered  0x001a   050   030   000    Old_age   Always       -       6566432
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       4
240 Head_Flying_Hours       0x0000   100   253   000    Old_age   Offline      -       20614h+04m+30.834s
241 Total_LBAs_Written      0x0000   100   253   000    Old_age   Offline      -       3951821603
242 Total_LBAs_Read         0x0000   100   253   000    Old_age   Offline      -       3756107205

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed without error       00%     12747         -
# 2  Short offline       Completed without error       00%     12745         -
# 3  Extended offline    Completed without error       00%      3721         -
# 4  Short offline       Completed without error       00%      3719         -
# 5  Extended offline    Completed without error       00%      3363         -
# 6  Short offline       Completed without error       00%      3361         -
# 7  Extended offline    Completed without error       00%      3000         -
# 8  Short offline       Completed without error       00%      2999         -
# 9  Extended offline    Completed without error       00%      1451         -
#10  Extended offline    Completed without error       00%      1311         -
#11  Extended offline    Completed without error       00%       613         -
#12  Extended offline    Completed without error       00%       550         -
#13  Short offline       Completed without error       00%       548         -
#14  Extended offline    Completed without error       00%       260         -
#15  Conveyance offline  Completed without error       00%       134         -
#16  Extended offline    Completed without error       00%        14         -
#17  Short offline       Completed without error       00%        12         -

SMART Selective self-test log data structure revision number 1
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Not_testing
    2        0        0  Not_testing
    3        0        0  Not_testing
    4        0        0  Not_testing
    5        0        0  Not_testing
Selective self-test flags (0x0):
  After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.

Maybe this is due to faulty SATA cables, or maybe my Seagate drives are finally approaching their ultimate fate.