During the flickering bit, what are you GI Sample grid (GI Sample level) settings and colour tolorence settings?
The grid should definatly be at least 4x4
I’d try tolorence of 2.5 initially (adjusting upwards (towards 10) until cured)
Then turn on “Show samples” and make sure GI is picking up the boxes in the distance during the drop.
If you have the sample grid set to 8x8 (default) then this is your problem, 8x8 as a size is simply too wide for an animation. You will probably get away with less rays when using a tighter grid and higher Colour Tolorance setting.
Apologies if you’re already using these settings!
It looks great though, box blur is much improved! The eyes are ace 
Ian
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.