Adding this comment to say that I think I encountered a bug. I made sure that everything was in order for a package, I applied the correct stamp to it, and yet when I tried to place it in the cargo it wouldn't stay in place, it kept coming back on the side. It either happens immediately, or if I place the package first and then try to change it's position, then I can only place it back to where it was before. And either randomly, by trying too much times or by clickling too fast, the package will just vanish. I think it's for either of the 3 reasons I listed because it only happens right after I encountered the issue of not being able to place it in cargo