Anyone having trouble with ANT+ dropouts read below. Zwift has been no help, but StagesCycling.com gave this advice and IT WORKS !!!
Routers transmit on the same 2.4GHz frequency as ANT+ (which is the power meter uses to communicate with the head unit), and can sometimes overwhelm the power meter signal. When this happens the head unit will not be able to receive the data and will display zero values, and then will return after the interference has passed.
There is an effective solution for this, which involves a quick adjustment to the broadcast channel of the WiFi router. Within the 2.4GHz band, there are even smaller channels present, which are numbered 1-13. Generally routers will broadcast on channels 1, 6, or 11. The ANT+ signal from the Stages power meter is broadcast on channel 10, which overlaps quite a bit with channel 11. Thus, if there are networks present on channel 11 it could cause interference problems. The easiest solution is to shift any of those networks on channel 11 to channels 1 or 6 to avoid overlap. Below is a diagram which offers a visual rendering of this signal overlap.
This is a fairly comprehensive guide on how you can make this change: http://www.pcadvisor.co.uk/how-to/network-wifi/how-change-wi-fi-channel-3325316/