I gotta say I'm super invested in your project. I can't really pay you anything (trust me I would love to pay for your beautiful work) but I am willing to act as a beta tester and give feedbacks and thoughts throughout your project.
about the janky physics... this is purely conjecture on my part but hear me out. I think there are three scenarios in which the boxes shoot out of the storage:
1. when the boxes get trapped inside each other or overlap in the same spot and the physics engine can't easily separate them from each other
2. the tank is going at full-speed -> the tank gets air -> the tank collides with the ground and goes into the ground -> physics engine gets confused and don't understand what it has to do
3. the tank rides over some sort of debris or junk which is similar to scenario No. 2
For scenario No. 3 what I would do is to detect at all instances if the tank is colliding with any junk, then disable the collision between the tank and the junk and see how that would play out. For scenario No. 1 I would keep track of "the number of collisions between boxes inside the storage". my guess is that when the boxes get trapped inside each other or overlap, the number of collisions peaks and we can detect that things are happening. I still can't think of a way to prevent it from happening though.
generally i think the reason that physics are this janky, is because the physics engine is handling most of the work. That's why I like to write my own physics and controller instead of letting an engine to take care of physics for me. it takes much longer to complete, but it's so much easier to debug
do you use unity? (or godot or unreal?)
also is there a way to contact you outside of your itch page? i can give you my telegram id or email or something. i don't think this is the most optimal method of communication