Why do you have both Deadlock's Stacking Beltboxes & Compact Loaders and Miniloader?
The deadlock compact loaders don't support loading into vehicles but the stacking beltboxes are very useful and that's why i personally run both mods but with the setting "Enable Loaders" unticked on deadlock's stacking beltboxes. This is especially useful for people who also use the optional mod called "Mobile Factory".