They’ve been getting caught in the teeth of the escalator when kids get off:

At rail stations and malls around the world, reports are popping up of people, particularly children, getting their toes caught in escalators. The one theme? The victims are wearing the soft clogs known by the name of the most popular brand, Crocs.
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One of the nation’s largest subway systems — the Washington Metro — has even posted ads warning riders. The ads feature a photo of a crocodile, though they don’t mention Crocs by name.
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According to reports from as far away as Singapore and Japan, entrapments occur because of two of the shoes’ selling points: their flexibility and grip. Some report the shoes get caught in the ”teeth” at the bottom or top of the escalator, or in the crack between the steps and the side of the escalator.