Zwift to Garmin export inaccurate

I just completed the Surrey Hills, doing more than 1000m climbing, but the Garmin export states only 170m climbing. Something wrong with the conversion?

It’s  an issue with Garmin and they and Zwift are aware of it.

BTW, elevation on a virtual ride means nothing since you are stationary. 

Thanks Paul. And yes, as far as I can tell, I do stay put when riding on Zwift!