Jerky navigation using imported blender skeletal mesh

I’ve imported a skeletal mesh from blender with a very simple skeleton (root, abdomen, chest, head, two arm bones per arm, two leg bones per leg and 2 feet with leg IK’s). When I apply this skeletal mesh to a character in UE4, when i do a simple move to the movement is very jerky and looks as though the character is trying to navigate around many tiny obstacles or something. However, using sk_mannequin skeletal mesh from the animation starter pack it navigates smoothly as expected. I also tried using no animation BP (so it just glides around like a scarecrow) with no change to the behavior. Switching navigation mesh → runtime generation → “dynamic modifiers only” in project settings fixes the problem, but why can sk_mannequin move smoothly regardless and my mesh acts all wonky?