When you're pulling out from a downline it is 1 extra G over pulling up from level. Check elevator throws, lateral balance. If it isn't either of those then check all incidences. Also, you can't compare doing a Wall to pulling out normally; the Wall happens so quick that you go deep into the stall before either tip has a chance to stall. Try pulling full up on low rates in level flight and see what happens. If it still snaps then decrease your elevator low rate.