Test is test, but always fly safe my friend.. if you notice anything weird, don't take the risk..
And to my own test.. with .550, I can say my Mavic flies more stably, And signal doesn't seem to have anything funny going on.. so I think I will stick with this one till that release something newer than .600.
As to the cache video, I tried without sound record on 4.0.6, took a total of like 12 vids and only one is unplayable.. so I Think
I can safely say this is an App issue, not the firmware.. I stand corrected if anyone else can find out another reason for this ...