Got this today for the first time. RCT715, Edge 1040 Solar; they're both about a month old.
Other connected sensors: Rally XC200 (also a month old), and a Polar H10 HRM.
The Rally pedals disconnected themselves early in the ride (cycling the sensor connection OFF/ON seemed to fix that one). Also noted that my Polar H10 popped a "low battery warning" perhaps 40 minutes before the Varia error above. All devices appear to be running current firmware.
Another thread with datapoints, here: forums.garmin.com/.../1424670