Because locking them on makes them function as numbers and therefore keys that Blockland will recognize ever since a recent update that caused some weird difference between Number Lock being on and it being off that also caused issues with brick shifting not working because people would play with it off or something
Unlocking them will cause them to work as Home, Up Arrow, Page Up, Left Arrow, 5?, Right Arrow, End, Down Arrow, and Page Down instead of the Number Pad equivalent that Blockland knows of and uses for bricks and whatnot
And this vehicle has functioned properly for me on the Number Pad with the lock on