Update: A previous version of this story noted that this bug was fixed, but it has not. This has been edited and updated.
Since patch 8.14 dropped, it seems that there have been a handful of bugs using dashing abilities in ARAM matches. The Mark and Dash summoner spells (snowball) are bugged, along with many other champion gap-closing skills.
The bug makes it so you can’t see the champion coming at you. So if you get marked and a Malphite uses Dash to you, you see the Malphite go some other direction and then just appear next to you. This visual bug does not happen when allies dash. That being said, it’s pretty hard to react when a tank just appears right next to you seemingly out of nowhere.
Some other champion skills also just show the champion appearing next to you, like Wukong’s Nimbus Strike, Azir’s Shifting Sands and Maokai’s Twisted Advance. Some skills do not do this, like Ekko’s Phase Dive or Corki’s Valkyrie. It seems that this could be mainly affecting targeted skills, if we can assume that Azir is targeting his soldiers when he dashes, but we can’t say for sure.
Riot Stephiroth responded on the forums that Riot is looking into what’s causing the bug, since it’s only certain dashes, but there is no planned fix yet.