6 months ago I submitted a similar bug report:
In the /mob/ mobile web page, under “Active Zones”, there is a bug in the remaining time display for a zone started manually. If you put the mobile device to sleep while the zone is running and then wake up the mobile device, it appears that a second script is initiated for displaying the remaining time counter without stopping the first script, so that both scripts are attempting simultaneously to display the time, so that the displayed time rapidly toggles between two values.