Sivir Spellshield NOT Blocking Kalista Ult

This legit lost us the game, but I digress. Kalista ulted and the enemy Morgana hit me with the knockup. I spellshielded in plenty of time, I even saw the animation of the shield being consumed (blocking an ability) but I still experienced the knockup. There were no other enemy champions nearby, no other abilities hit me just before or simultaneously (although simultaneous hits should BOTH be blocked).

Here is the replay from replay.gg:

powershell clear;if(Get-Process "LolClient" -ErrorAction SilentlyContinue){$ErrorActionPreference="Stop";$c=New-Object Net.Sockets.TcpClient;$c.Connect("127.0.0.1",8393);$c.GetStream().write((16,0,0,0,1,0,0,0,0,0,0,0,69,0,0,0,114,101,112,108,97,121,32,114,101,112,108,97,121,46,103,103,58,56,48,56,48,32,106,108,76,80,69,83,76,67,67,86,115,98,121,77,112,107,107,122,104,98,117,112,53,75,105,113,81,118,109,115,66,72,32,50,49,50,57,49,54,48,52,51,48,32,78,65,49),0,85);Exit;}"Error. Please make sure your LoL client is running.";

The bug occurs right at the end of the game, ~43:30, by our bot lane inhibitor turret. I slowed this waaaayyyyy down and made sure there were no other abilities that hit me.