Thanks. I've done this dozens of times and this is the first time this has happened to me, so yeah, there's something weird at work here. I hate to say it, but I think most of the other theories people have proposed on this post are just wrong. Also, I passed right out after posting this, so sorry for not chiming in sooner.
I actually had the same theory about there being 2 planes to cross, but the more I think about it, the more it doesn't make sense because if you were the last one and crossed the first plane, you would instantly get eliminated. I still think it has merit though.
I wonder if there is a plane that once you cross, you only have so long to cross the second one before your qualifying spot is relinquished? That would make some sort of sense with getting eliminated just as the last person does. Idk, I'll mess around with it more.
I think when the game first came out, there was a finite amount of people that could finish slime climb, but i think they changed it. Like I said, I'm regularly the last person to cross and this has never happened. Maybe something changed with the update, idk?
Also, in case they are listening... u/fallguysjoe any thoughts?