The rest was my first thought as well, but Im shooting on a dead solid padded rest. I rest the pistol right in front of the trigger guard every shot, same position every time as is recommended with the Contender pistols.
Repeated tests showed the same vertical stringing with the same loads that strung vertical before. The results were the same and showed that once you hit 35 grains with the charge...the vertical strings stop and you actually start shooting groups.