In newer quests, rings with a damage divisor of 0 seem to be malfunctioning in different way. Oddly enough, they still work perfectly fine in older quests.
In some quests, it causes Link to take normal damage, which seems to be the case in LOZ-Generation5-3.qst, while in other quests, it makes Link immune to damage even if Link doesn't have enough magic/rupees for it to have any effect, which is the case in bosstest.qst. However, peril rings with a damage divisor of 0 still work properly.
Power 0 rings malfunctioning in newer quests!
Should be fixed now.