Unfortunately i dont have a screenshot since it was the crucible, but i think it does not really matter.
In the birch level of the crucible, at the topmost platform. I activated the rune plague breath. although from the stairs, what is slightly lower in altitude.
As normal the character jumped over to the desired location, did its dmg, killed the enemies, but…
It somehow spawned my character position at the same elevation as it was before but now at the new location (about one knee length lower than the platform)
As a result, the platform was not recognized as collision and the character fell through it to its death.