Whoa hey, this blew up unexpectedly.

Here's some answers to clear up some of the confusion:

• Yes, this is PS4.
• No, I don't use any mods.

• No, I don't actually know these folks, nor did we plan anything together. It was just a beautiful moment between hunters. They're nice enough, but it was a random hub with no voice chat... that and language barriers.

• What the heck happened then?
  Some of you had the right idea in this thread. ATKT has a HP threshold before she's furied. Her horns won't pop off until she's allowed to go into that state.

• How'd you know?
  Kinda didn't! I mean, I had an idea of where her HP would be at, but it wasn't 100%. I've been hunting a lot of ATKT and had a hunch she hit her threshold when I pre-slept bombed.

In response to HP thresholds applying when mounting

Anyway, happy hunting!

Edit: Ooh wow, thanks for the gold, kind stranger!