High Offline_Uncorrectable and Current_Pending_Sector, yet no reallocations or read errors

Question

I have a SAMSUNG HM160HI in my laptop at work. This hard disk produced some read errors lately. I reinstalled all Ubuntu packages and my private files don't seem to be affected. Knowing that hard disks replace defect sectors that previously caused read errors with spare ones, I was hoping that the read errors would go away - which they did! I can read the whole hard disk sector by sector without a single error.

Now what doesn't make sense are the S.M.A.R.T. attributes of this disk:

ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   100   100   051    Pre-fail  Always       -       0
  3 Spin_Up_Time            0x0007   252   252   025    Pre-fail  Always       -       2062
  4 Start_Stop_Count        0x0032   002   002   000    Old_age   Always       -       998454
  5 Reallocated_Sector_Ct   0x0033   096   096   010    Pre-fail  Always       -       41
  9 Power_On_Hours          0x0032   085   085   000    Old_age   Always       -       8160
 12 Power_Cycle_Count       0x0032   095   095   000    Old_age   Always       -       5458
191 G-Sense_Error_Rate      0x0032   065   065   000    Old_age   Always       -       359719
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       66
194 Temperature_Celsius     0x0022   115   070   000    Old_age   Always       -       41 (Min/Max 11/56)
196 Reallocated_Event_Count 0x0032   100   100   000    Old_age   Always       -       36224 (0 6)
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       4332
198 Offline_Uncorrectable   0x0030   100   100   000    Old_age   Offline      -       13478
199 UDMA_CRC_Error_Count    0x0036   252   252   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x000a   252   252   000    Old_age   Always       -       0

The Offline_Uncorrectable RAW value doesn't go down, it goes up! It used to be 12.9k, now it's at 13.2k. Yet, I don't experience any read errors. The Current_Pending_Sector value also goes up. And the Reallocated_Sector_Ct does't move one bit, even though the hard disk had plenty of opportunities to reallocate the sectors as I was reading out the whole hard disk. I was even copying the hard disk onto itself just in case sectors are only reallocated during write operations.

So what's going on? The hard disk is not reallocating broken sectors in spite of the fact that the firmware is reporting 4k sectors that are pending to be reallocated. Why do I not experience any read errors even if I read the whole disc, sector by sector? Why does Offline_Uncorrectable not go down, since there are no read errors anymore?

Has anybody experienced anything similar?

The hard-disk will be replaced soon. Yet, I have to live with it for a few more days and the erratic behavior puzzles me.