It will depend on the ratio of lateral to vertical speed. And this is not going to be full-blown VRS, but it could be that even marginal loss of lift from a severely under-performing prop is enough for the aircraft to lose stability.
I've decided to add pitch to my props, just to see if what you're saying is really like that. Yesterday, last night I was watching Dad of Random Channel on YouTube, he flew out his mini to the top of some mountain and then he visually turned around without looking at his map and came home completely the wrong way like over 70 degrees off. Anyway, his Mini did the same thing, just uncontrolled descent, although his battery was already low.
I was thinking can this be a combination of an abused battery during the flight, and also abused drone!? I've seen these videos and also read of people complaining that they power up their drone, take off, switch it into S mode immediately and just push the stick forward all the way! They fly at the maximum speed the lil fella can get to, and they do this for extended periods of time. I think that they have charged their battery like 3 or 4 days ago to 100% and then not flown it, and then because of the time passed with the battery being fully charged and not used - it starts to discharge and lose its ability to deliver good current also! So they basically abuse the battery and drone, at start of flight battery is 91% or something, then the full speed forward in Sports mode, kinda drains the battery in its currently weak state even more. After that the Drone now just needs a tiny little bit of VRS or just "fluffy" air and the uncontrolled descent begins! Even a down command should be able to initiate this type of descent if I'm correct.
I also think I may be right because when the drone is restarted it seems to fix this issue for a while. so this may be because the battery had a small good rest - to regain some of its current sending abilities, until the next time all this repeats.
So I say its a combination of the battery not being able to deliver enough current when abused and the abuse of the actual Mavic Mini - expecting and forcing the little drone to fly like its bigger siblings is not correct. This is not a Mavic Pro or something, it should be used with caution and not abused.
as always - all the above is just me thinking, so don't take anything for facts..
cool cool