I think it depends on the tree and how you set it. I've never folded it up. It can happen on any platform that cams over with a post. If I ever think there is a concern about it folding I can run Amsteel on those lower tabs to keep it from folding up.
While true any platform with a post can kick out the further out the pivot point is the easier it is to get it to fold up. The Mission post is set much closer to the tree so it takes a LOT of effort to get it to start to move. I think you'd be hard pressed to get the Mission to fold up and kick out as I tried as hard as I could to get it to do that and it only moved about a half inch and then stopped. When i stepped back on it it only cammed even harder to the tree.
But i have seen the Ambush do it and completely fold up with far less effort. Maybe they can move it back a bit with a Gen 3 model? Nice to see they beefed up the Post though to hopefully mitigate the snapping post issue.
I do like these bigger platforms as i never noticed a difference packing in something 3.5 pounds vs 5.5 pounds as its not like im out West carrying it for miles and miles every day for 7 days in a row. Its more like walk in a mile or two, hunt, walk out and go home when whitetail hunting so for the 3 to 10 hours im hunting out of a platform/stand id rather be comfortable as opposed to carrying 2 lbs less while walking in/out that mile or two.
Its all a far cry from the 35lb stand and steps i used to carry in and out to hunt public every day in the early 90s!