No problem with my Fenix 5 Sapphire, connected to my phone within a 5m range ...
Same really bad experience here - with my Fenix 5 Sapphire (and Samsung Galaxy S7). I owned Fenix 3 previously and (after several firmware upgrades at the begging) the connection was really stable. With Fenix 5 it is nightmare. It loses connection and reconnects gazilion times a day. I wear watch on my left had, and typically I carry phone in my right back pocket of jeans - this causes loosing connection and re-connecting all the time. Sometimes I even experience the connection lost when a sit at the desk, having watch on my hand and phone lying on the desk. This is not acceptable.
How is other people experience? I truly hope this can be fixed by FW upgrade, in other case I will have to return this unit.