I was flying high in the sky, full durability on the Unb3 elytra, fully enchanted netherite armour, full health and hunger, no chunks were loading under me tho, at some point i die and i get the "player fell from a high space" death message. 

The world i'm playing in was generated in 1.12 but i have since played without any major issue. The chunks i were flying on were newly generated, maybe that could be involved with this strange bug.