Same problem for me. Took me a good three-four emails to support before they even got in the ballpark of understanding the issue. Then just suggested the old uninstall-reinstall which doesn't work. How about "fix the app!!!"?
The app starts a preheat timer, but then uses that as part of the cook time, so once the temperature is reached, the app thinks that it's been cooking for ~13 minutes so the timer on the app is wrong. Interesting thing is that the timer on the Anova itself works properly.
I'm on IOS with the wi-fi model.