The fix depends on which 105 headset you have. The old ones (HP-1055) used loose balls in retainers. If you have one of these, remove the retainers and replace the balls with new loose ones, adding the few more needed to correctly fill the races. That will change the ball spacing so the balls no longer line up with the pockmarks and will buy you a little more service life.

If you have a newer 105 (HP-5500), it has cartridge bearings and you will have to replace the cartridges. A temporary fix would be to switch the top and bottom cartridges (they are identical) so the better cartridge is on the bottom where the load is concentrated.

The most certain fix is a new headset and 1" threaded ones are still easy to find.