Why is my AirTag showing as nearby when it's far away?

I have just added 2 new airtags to our account but both are showing up as nearby and 'Now' even though they are both miles away with my wife!? It has stayed like this for several hours and yes I've restarted the phone, tried different devices, and made sure both phones are up to date. Also all devices have bluetooth enabled.

How can the device be showing up as nearby when its about 20 miles away. I've even tried activating lost mode but all that happens is after a couple of minutes I get a message saying device found and that its 'nearby'!!!

One airtag I could put down to maybe being a bit dodgy or something but 2 behaving the same! And yes before anybody else asks they both had new batteries put in yesterday (not the duracell type coated ones).

Any ideas?

Thanks

[Re-Titled by Moderator]