NHS Track & Trace App Issue24 Sep 2020 14:33
Apparently, once you 'check in' somewhere, using the app, there's no option to check out. Unless you check in somewhere else, you're shown as being at that place until midnight.
So you might go to a cafe for breakfast but, because you can't log out, if someone comes in during the evening with Covid you'd be told to isolate - even though you'd left hours before.