Those swaybar studs are round-head 'bolts' tack-welded inside the crossmember. The only way I found to fix this was to knock out the spot-welded head, then drill into the crossmember from the ZF side and use a real bolt & washer thru your drilled hole. Be sure to size your drilled hole for socket clearance so you can hold the bolt for tightening.
Trying to weld-repair a broken stud doesn't hold very long- possibly because weld heat anneals the result, which was too small & weak to start with. With a real bolt you can go to the next grade and size up and be much stronger. The fix is invisible to all but people who've had this happen.