We are aware of this issue and are actively investigating it.
If you do have this happen to you, your end-of-hunt rewards should still have been added to your account (even if it looks like they were not at the time).
Breaking Shrowd’s tail while it enrages can cause it to go invisible and unhittable
This issue has been reopened We thought that we had fixed this in the 1.2.0b hot fix, but reports are coming in that some players are still experiencing this. We are actively investigating.