Setup another user, iPhone presence not working

Have setup another user in family, all logged in etc correctly. Added his iPhone as a presence. It’s only seems to be working when he arrives not leaves though.

I can’t rely on this yet for smartapps if it’s this unreliable. Is it me, ST, iPhone or what.

Anyone else have the same? This is a trial before I add the rest of the family’s iPhones to start controlling some apps…