I am weaving Summer and Winter on 24 shafts.  A four pick block is 1+2, 1+x, 3-24, 2+x.  X can be 3-22.  23 and 24 weave background.  On the last pick of the block, 24 will sometimes rise.  Sometimes I can stop on the left treadle, which will drop 24, I can then bring up the correct shafts.  Sometimes this doesn't work, I have to bring up 24, reverse, which gives me the correct shafts, etc.  I think this is caused by not clearing pick 3 (3-24).  The adjustment for the left treadle is maxed, and swaged to the cable.  Anybody have any ideas?  All I can think of is to take the turnbuckle apart and shorten the eyes with a saw. 

Check the alignment. Perhaps the pin for 23 is sometimes also catching 24. Sometimes reversing will cause the alignment to re adjust that tiny bit.

Aha.  I didn't think that these cables would stretch, but that would explain it.