After several storms with lots of rain and high winds about 20% of my G41 snapped at the rootstock too. These were 2 year old trees with about 30 apples per tree. Each tree was clipped to tight trellis wires starting at about 3 feet. The graft joint must have been very brittle and prone to failure since these trees were well supported and not overloaded with fruit.
Also lost a whole row (25 trees) of 2 year old G11 trees because of a trellis failure. These trees were 10 feet tall with a good crop. The “deadman” support post which was 3 feet in the ground with 80 pounds of concrete on the hole at the end of the row was pulled out of the ground. None of the G11 trees snapped and if I can get the trellis back up I believe most of the trees can be saved.