I'd open it up and take a look. The adjustable cup shouldn't thread in that far so either there is an issue with 1) the bearing balls (too few or too small), 2) the fixed cup has loosened and is working itself out, or 3) you're using a spindle for a 68mm BB in a 70 mm shell (unlikely). The amount of threads exposed on the NDS cotter may mean that it is a replacement, which means that someone had it apart before, which leads to 1) above as the most likely.