The Milwaukee M18 saws come with a 3/8"pitch, low profile, .043" gauge narrow kerf bar and chain. Since they are thinner than a regular bar, they tend to be more flexible. I suspect that it is the bending that causes the chain to derail. You really can't put much side load or twisting pressure on them. It takes some adjustment for those used to dealing with regular kerf bars. Some people never quite get used to how comparatively gentle you have to be with them.
The replacement is a 3/8" pitch, low profile, .050" gauge bar and chain. This is a standard kerf bar, so is thicker and stiffer than the narrow kerf bars. This chain uses the same drive sprockets as the narrow kerf chain, so it's not surprising that you are not seeing unusual wear.