Apple watch not displaying miles on bike ride

Hi

I have a Apple watch series 3 paired with a iPhone 11.

When doing an outdoor cycle ride the display is stubbornly refusing to display the distance covered in miles, just kms.

I've changed the Unit of Measure to miles on the watch and phone.

The Health app is in miles.

I've also reset the watch and phone and set them up again from the iCloud backup.

When I connected the apple watch to an old iPhone 8 the watch will display miles.

I'm thinking there is some setting on the phone that needs adjusting

Any ideas as it's most frustrating doing a bike ride in kms