I can see the bite mark on the tooth which causes the chain to start coming off. Fortunately this happens only when the crank is rotated backwards. Visually, I do not see anything wrong with the tooth. The entire crank wheel seems to be in one plane. The crank has four small screws. I am not sure but they must be the one holding the plastic cover. If I removed that cover, I will be able to get a pliers on the tooth but I really don't see it is bent or anything like that. I do notice some play in the crank itself. Mind you, this is a "classic" Huffy, 25 year old, US made, department store bike but I can raid parts from the other one which we retired after purchasing a "real" bike for my wife. Two gears on the front and this happens on the bigger diameter wheel. The rear gear does not matter as far chain slippage is concerned.