Every time I do the Marksman's pass level, I find my creations colliding with an invisible object located a short distance in front of the ramp, between the bounding box and said ramp.

I'd estimate the object to be roughly 3x3 squares wide and 1 square tall just one square large perhaps, and exceedingly difficult to climb over (most of my vehicles partially shatter or get completely stuck on or against this invisible object).    In order to make it to the ramp I wound up having to drive around the object, and it's a pretty tight squeeze between it and the ramp.

Strange that I haven't seen any Let's Players slamming into this thing..  I encountered it both in the stand-alone humble bundle download, and just now in the steam-installed version.