Anyone found a tortilla that doesn't crack in a warming drawer?

We switched suppliers in June and the 12 inch flour tortillas we're getting now split along the fold about one in five times, especially later in service. Same steamer, same temp, same technique from the same three cooks who never had this problem before.

I've tried lowering the heat and adding a damp towel, which helps a bit but not enough to stop the complaints. Before I go back to the old supplier at a higher price, has anyone dealt with this and found it was something other than the tortilla itself?