[GAMEPLAY] Elder dragon execute bug with Tahm Kench.

Description: In a game as tahm kench with roughly 400 armor I got hit by caitlyn to (2153/3148)hp and the execute dmg of the elder dragon was triggered. The grey hp bar at the time of the execute was about roughly 20% of my hp. I encountered then a similar situation later in the game when I got executed with 1800/3400 hp left.

Reproduction: Currently I was unable to reproduce the bug since the Servers were down.