I have Infinity 2 and the latest Hub 6
My Hub 5 dropped off both of my laptops (both Windies 10Pro, one Lenovo and one Fujitsu Siemens), I also have a Windows/Nokia 535 smartphone that also dropped off the Hub 5 and went to the BT-Fon
Since upgrading for free to the Hub 6, all three gimo's have stayed attached to the main Hub 6 and not wandered off...and when I travel with laptops and phone and return, all three latch on to the Hub 6 without issues
I got my Hub 6 from BT after complaining about the behaviour of the Hub 5 and they sent an engineer round to check everything and without identifying or confirming the issue they upgraded to the latest Hub
Which makes me think there could be an inherent fault with the Hub 5
I would suggest you complain loudly to BT and have them upgrade you FOC to the Hub 6....stamping foot and yelling if need be