Well, I’ve just been through the whole thing in slow motion and I see what you mean, firstly, you do need more blur samples, try the automatic mode as that may well fix all these problems, though, I must confess to never having seen a blur carry away parts of a frame as happens towards the end of your animation - the cubes over the tree that seem to disintigrate are simply bizarre!
I wouldn’t try a seperate pass for the tree until I’d experimented with the blur sample setting as I can’t see that being a cure, though it might make the issue less obvious. Someone with more blur experience should step in 
I’d like to know what your GI settings were as it’s a nice stable grid you have there ?
Amazing compression on the movie by the way.
Ian
PS. Attached a screengrab for others as a quick refrence.
I want more character capabilities in this program. Period. Its my belief that character enhancements will be the biggest draw for new users than any other function.