Invincible ape ape in waterways

I was followed by a very small, angry, invincible ape while in waterways. It still dealt damage to me but I was unable to target and/or hit it.

I too have encountered this angry, invincible ape (Feral Primate) in the water ways. It also targeted minions. I have linked a picture of the little annoyance and circled it. I too could not target it or cursor over to find out what it was. I tried resetting it by going back to town but that didn't work.

[https://imgur.com/a/bSiDu3c]

Happened to me as well. No triggering event. Just came out of the bushes and hammered on me until I died. Hits quickly so you can't even town portal to leave.

Very similar issue in Waterways.

There were two River Drake that I could "kill" (to zero health). They would look dead then immediately revive. I could not kill them completely without them instantly reviving.