I’m having the same issues
It looks like it’s hunting for days when the area is already downloaded in offline maps.
I raised this with OS as a fault and they said it’s set up to download the latest maps and to turn on airplane mode if you want it to use previously downloaded maps. This is a pain if you ask me, especially as I use Strava Beacon to let my wife know where I am. Also, the “latest” OS maps are often 10 years out of date so it’s hardly likely to make any difference.
I also have an issue with the red arrow showing where you are pointing in the wrong direction. For example, it shows you facing south when you are facing north! Needless to say, this is about as confusing and potentially dangerous bug as can be imagined. I haven’t found out whether it’s a problem with the app or a bug in the iPhone’s internal compass.