My partner's location is showing wrong on Find My

So my partners phone says that they were in another city and it could maybe make sense that they weren’t but I just don’t understand how the location could be that off , it kept moving and following a certain route I just want to know if that’s possible or if they were actually just in that city

the location only loaded for a bit and then it would go blank again and says no location found

[Re-Titled by Moderator]

Original Title: Wrong find my phone location