Bug seem to be random. Not sure if it connected to workshop missions only. Try my mission Whole Lotta Altis with saving, exiting and resuming the mission:
http://steamcommunity.com/sharedfiles/filedetails/?id=173155826
Here is savegame from the mission once having the problem (from saved\steam, folder name was [dyn%2fsp]%20whole%20lotta%20altis.altis). I have already taken enemy weapon and vest at this point but the bug can be still there.
https://www.dropbox.com/s/xiujw39y1zkqs6m/%5Bdyn%252fsp%5D%2520whole%2520lotta%2520altis.altis.7z