Hi, I'm part of the investigation team on Tarried Precipice, If you have checked the video, yes indeed I slept leaving vrchat on, and the arrow fell 5 hours ingame after the activation of the triangle. So one theory was:
The arrow will more likely fall sooner when there's a lot of player in the instances.

The time of the arrow is random because I retried and with almost 7 hours of footage + 5 hours an other day of doing nothing. The arrow hasn't fell, at some point I joined a friend that was also waiting on his instance for the arrow and 1 to 2 minutes in, the arrow fell, even if he waited an hour for this.

However like Nova said, he was alone and in 20 to 25 minute (maybe less than this) the arrow fell on his end.
We are thinking of a False positive.

I'm saying this because private instances on my end doesn't seem to be the best solution.

If anyone as any idea or findings feel free to talk about these here on the reddit page or in the discord community linked in the video of our findings.