Often, after teleporting into an area with mobs, the mobs are invisible and impossible to hit - but are still hitting you. Logging out and back in fixes this.
Probably a loading issue.
Possibly related to other players being invisible after teleportation.

Observations:

1)
In survival mode, fought mobs and was killed. Teleported back to the area, all the mobs were invisible and couldn't be hit, but were still hurting me.

2)
In survival mode, fought zombies and was killed. Switched to creative, teleported back to the area. Saw a zombie attacking a testificate, and the testificate taking damage and being killed, but I couldn't hit the zombie and kept knocking out blocks behind it. (Poor villager, I tried my best to save you )

PS: (unrelated)
Shouldn't the "Pick the game mode you were playing (eg. Creative or Survival)" part at the issue creator include Adventure Mode?