#1 - May 7, 2016, 2:43 a.m.
Now, in the last hour, I have seen;
1) A grotesque gold enemy not drop globes upon death - he blew up, then his character model just stood there and did nothing (could not be targeted, but blocked my way).
2) 3 instances of grotesques becoming invincible and untargetable
3) Grotesques vanish upon death, and seemingly not grant any progress.
Please look at these things, there's something VERY wrong with them at the moment.
Update: 4) Grotesque elites can sometimes die normally but leave an invisible hit box where they died that you can't move through, as if a monster was still there.
Update: 5) Grotesques can not only become untargetable and still hurt you, but also become INVISIBLE. Pray to RNGesus that you don't see this one if you're in HC.
Updates 6, 7, and 8;
Grotesques can sometimes not drop loot in normal rifts if they are elites.
Elites that are the target of a bounty can make the bounty un-completable if they experience the bug, which ruins the whole bounty set.
Unconfirmed; grotesques can cause issues in set dungeons by not counting as being dead when invisible and untargetable, making the objectives impossible to complete.
Update; fixed as per patch notes. Big thank you to blizz for fixing it.