Glitched Mobs

Hello,
Whenever I initiate combat with a pack or multiple packs of mobs I cannot heal, use potion or hit anything until the first aggro'd mob is killed.
This only happened after recent maintenance.

Becomes increasingly frustrating when you aggro something that doesn't follow and you find yourself sponging enemies without being able to hit until you reset their aggro and the original "ghost" mob.

Thank you