Fusion Hybrid Cruise control cancels itself when driving at highway speeds.

Intermittent problem, driving at highway speeds with cruise control on and speed set, for no apparent reason the cruise control shuts itself off (panel lights for cruise control flicker and go off at the same time) . Press resume and nothing happens. But if I press on button system comes on, speed can be set and panel lamp comes on as normal. Sometimes on trips system works fine, other trips the same intermittent problem occurs.
Fusion Hybrid has 11,000 miles, problems has happened occasionally the last few weeks.