We’re currently deploying a hotfix (18.4.1) that will address the following:
Reduced client lag in Battlegrounds caused by Elemental buffs and animations.
Fixed a Battlegrounds bug where Seabreaker Goliath Mega-Windfury would not activate.
Fixed a bug where the Witchwood Adventure would not appear in client after being redeemed from the web shop.
This fix will take place on the server side, so you will not need to download anything if you have already updated to 18.4.