Rider dismounts even thogh wheel is still 'coasting'?

Wondering why my rider up and ‘quits’ when I stop pedaling (but my wheel is still spinning).    Is zwift only using power and cadence information to determine speed?

Thanks

That depends on your setup

I’m guessing it’s ERG mode that causes this?

 

If not, what ‘setup’ will allow me to keep moving when my wheel is spinning?  I’m on Kickr Snap.