Zwift closing without warning

Had this issue before, seems intermittent. Today the app just disappeared as I was getting near the end of a run.
Any clues as to why it does this and why it only happens occasionally?

What platform do you use to run Zwift?

I use Macbook Air

having the same issue i have yet to complete a single training ride. sometimes minutes in, dont even finish the warm up sometimes about 40 minutes in. running windows 10