Confirmed as of today.ran into the same bug, no drops for 3 turns of the metai followed the advice about separating from the zerg and hitting the last one solo, instant pop! thanks for the pro tip. P.S. if you have a big zerg, u need to be careful about the mobs as they will obstruct you from hitting the plagued sac and you will need to take them out first. They will however be veterans with big HP bars , so recommend getting your stuff for this venture :)