Corpses located on navpoints seem to be treated as insurmountable obstructions by the AI under many circumstances. This isn't always the case, although I suspect that has more to do with the body not blocking the nav path/point/whatever even though it may visually appear to do so.
Often this happens in chokepoints- someone dies moving into a fenced area through a gap, their body falls across the opening, and then the rest of the AI squad say they are "unable" to move through the gap.
However I have had this happen out in the open in intersections as well (see pic). Since there seem to be very narrow nav paths for the AI to follow, if they think a dead body is an obstruction, then whole intersections and bridges get blocked pretty easily.
To be very clear- if you teamswitch into the AI that is refusing to move through the gap, you can easily move over the body. {F22873} {F22874} {F22875}