Happened to me as well last night.
To mine better underground I used /back to have help with the Haste2 of my home base’s beacon. One of those /back’s killed me instantly for “Fall Damage”.
Hard to reproduce, as it was just one out of many. Tp-ed from a stone block to another stone blocks with plenty room above.
Sorry, I was not recording and have nothing to show – not even my vanished Gset !?! :/

Hope you guys can catch the /back/tp/home- Monster !
Baz