Key Fob for Model Y

[WllXM]

There has been chatter of a different protocol (sorry, forgotten the technical name) which is able to deduce "distance" rather than just "Connected / Not connected", and clearly that would be better.

That would be UWB. Rumours that it's integrated into Highland but nothing confirmed just yet.
Would be great as this is the protocol Apple uses for CarKey and would indeed allow less battery drain.

I also think that the recently introduced "Activity mode" option (again, forgotten the name, sorry) may help. I said DISABLE on mine when I installed that update (and I now can't find how to change that anywhere), but (from subsequent reading) I think that may be intended to detect when the phone isn't (hasn't) moving, and then disable unlock (and/or save some battery). Sounds like, from your test (i.e. phone had sat still in upstairs bedroom for some time), that wasn't the case. Might be something to consider - if you can find the option!

Just go into Settings on your Phone, scroll to the Tesla app, and enable the Motion & Fitness toggle

 

[WannabeOwner]

Settings on your Phone, scroll to the Tesla app

Doh! Like a complete Rodney I went into Tesla APP and looked in OPTIONS there ...

Thanks