There seems to be increased instability with the PC app as this is the second time recently it has just frozen.
I can live with this despite the annoyance, but it would be a lot less annoying if it didn’t lose any progress you’d made towards the challenges, which it seems to be the case.
This was during a ride (and not at the end or saving or anything like that.
We haven’t seen any new issues come up since the last update, so it’s likely this issue we’re still working to fix. I’d need your logs to confirm, so submit a ticket via bit.ly/zwiftsupport if you’d like us to look at the freeze.