Am with JW411 (quite literally) all the way on this one. In the early days it was found that the clay, (a component of this and most greases), was to a degree hygroscopic, and in freezing conditions the grease "firmed-up" and stopped the flaps deploying. A change of spec, some experimentation as to how much and where, saw the problem solved.
As the usual lock-out occured immediately when deploying from flaps zero to any other setting, (so they never actually moved), we pilots also contributed to reducing the problem. As a lock-out is caused by a sensing of the degree of resistance to movement, we simply unloaded some of the aerodynamic load by selecting flap at a speed well below the book limit for the amount of flap being selected, (within minimum manoeuvring constraints of course).
It worked. Maybe present-day drivers might like to consider this rationale if the problem ever starts occurring in their fleets.