daily GPS failure

Hello, world.

We have a Canopy cluster of six APs(7.2.9, sw sched.) and a standard CMM (not Micro). A week ago a problem arose: once a day all of the APs lose their sync to the CMM’s GPS module for 15 minutes, thus paralyzing the whole network. What can that be? GPS module defect, or RF interference, or some software failure?