This morning my watts kept dropping to 0 - intermittently. The first thing I tried was moving the ANT+ dongle closer to my trainer (Tacx Bushido) - but that had no effect.
Being a techy sort I had a think what had changed in my setup. The only thing was I’d put a wheel magnet on my wheel (for the Garmin speed sensor). After removing this everything worked fine.
I’m not 100% that this is the root of the problem I was having but removing my wheel magnet seemed to sort it.
For the record I use the GSC-10 for my cadence on Zwift as I can’t really see how a turbo could calculate cadence accurately. As a rule, this works fine.