As above, the cold is most likely. I'm guessing you went on the plinking range after taking the rifle out of a warm car after being in a warm house. But then after checking all is good on the plinking range it probably cooled down a fair bit before you went on the course.
I'd avoid grease on the shuttle at all personally and run it nearly dry. A bit of dri-slide buffed in or a tiny bit of light oil.