Pretty old thread but I could just as well respond and use the thread for info on this bug specifically.
It's a pretty wierd bug that only a handful of people seem to be getting. Nobody knows how to replicate it and someone mentioned it may be a compatibility error with another mod.
Along with that, it seems that loading a new game seems to just fix the issue.

If anyone else seems to have issues regarding this please mention it along with the list of mods you're using at the time.