I had the exact same problem, lost some stuff too. I would go over a bump and the bottom would pop up and the contents in the basket would fall out.

My solution was to go to Walmart and get a screw type locking carabiner. When I have the basket open and anything is in it, I unscrew this carabiner and wrap it around the bottom of the floor and side panel and it prevents the bottom from flipping up and the contents from dropping out

also zip ties are your friend for the rattles