The US Air Force Mod and CUPS Terrain seem to be having an unknown error between them after the 1.56 update.
Run the two mods and place any soldier you can control in a map, then try to run and turn. The soldier changes stance automatically and seems to kneel whenever you try to move too quickly. Thought it was a "feature" or something with the new update, but does not seem to be the case when CUPS runs by itself, or USAF runs by itself.
I'll inform the owner of the USAF mod as well of this collision, but I figured I'd see if the larger CUPS community is able to recreate and verify this issue.