I've found I can minimize spillage of the open boxes with items inside by crouching first, then grabbing the crate. It's pretty consistent.
You can close boxes with left click, items wont move into the box.
gotta remember to check date of post Skar.
33 days ago - you couldn't close boxes - That's a recent feature. - Lifting with your legs and not your back was the best/only way to reduce physics explosion pre-0.0.82