Repro:
1. Pick Elder Titan and level up Astral Spirit
2. Cast Astral Spirit
3. Wait until it starts returning
4. While it returns, die
5. Use buyback immediately
6. Cast Astral Spirit again

Result: The spirit does not immediately return to Elder Titan when he dies while it is flying towards him. Instead, it just gets hidden as normal and has to travel all the way back to ET no matter how far he is. If Astral Spirit gets now cast again before the spirit reaches him, it will not appear at the cast location, but will still be traveling back from the previous cast and be visible again.

Expected: No matter the timing, the spirit should always instantly return to Elder Titan when he dies.

In the video, I locked the camera on the spirit to show how the spirit has to travel all the way back to Elder Titan. The ent_text command could also be used to make it visible.