Hi there,
Quick message just to share my experience with quite often dropouts with ANT+ devices causing freeze in Zwift.
First my setup:
- old laptop (Intel Core i3 @2.20GHz, 4Go RAM, GC Ati Radeon 6470m 1Go)
- Tacx Neo Smart
- Garmin HR (not the Dual ref)
- cheap unbranded ANT+ dongle (15€)
All devices connected through ANT+ (not Bluetooth or ZC).
With this I always had freezes, some seconds to some minutes (!), happening around the 40-45min of ride sessions.
Zwiftalizer reported, as expected, connection issues with all my ANT+ devices.
So I firstly reworked the setup by adding a USB cable to move the dongle close to the Neo (which was btw initially already close to since the laptop is just in front of the handlebar). That didn’t fixed anything.
Then I challenged my dongle, indeed, whatever the USB port in use and whatever the PC, it was always using 100mA as power (value picked from the DeviceManager). But my dongle worked just fine with a friend setup… so dongle not in cause.
In fact what I finally noticed was the RAM consumption, always reaching the max when the dropouts happened. After having tried to reduce the Zwift settings to their minimal, and made sure that Zwift process was the only RAM consumer, I bought 8Go of RAM to exclude this possibility and upgrade my laptop. And this has fixed the ANT+ dropouts! 1,5 hours of ride yesterday without any troubles 
Hence my conclusion about the minimal specs described by Zwift, 4Go of RAM is clearly not sufficient (or not anymore). The doc should be updated to avoid user waste their time with poor PCs.
