"Crawling" under a  solid block in a BDS-hosted world results in immediate damage (from suffocation?).

It occurs when crawling as well as swimming (diving? whenever you're horizontal), when approaching a 1 x 1 space with a solid block on top. Ex. when mining, you can crawl through a space with a trapdoor but subsequent stone blocks will cause you to quickly take damage in what I can only describe as suffocation. It appears the game doesn't account for the head location change in horizontal vs. vertical navigation.