Flex2 Not showing walking distance or map properly - How to make sure GPS is on when screen is dark?

[sag621]

I've been here twice to post this problem with my Flex 2 / Fitbit App.

For more than a year whenever I walk the App tracks and shows how far I walked and other stats. As of about a month ago it no longer shows exercise (walking) distance or the map properly. When I walk it only tracks when I have the screen on the phone on. When it goes off, it stops tracking. If I keep it on (hold it), it tracks properly, shows on the map on the screen, and logs the distance.

If I turn off the phone while I'm walking, and turn it back on after a while, it will map from where I turned if off to where I turned it on in a straight line - like a bird flies - where you can't walk (see screenshot links below).

The other day I took my walk (~2½ miles) and intentionally kept in in my pocket. When I got back home and tapped the screen to end the walk, it gave me this,

When I tapped DISCARD, it put "Are you messing with me?" up on the screen. Cute.

A while back I used an older phone (Moto g5+) that did not have the problem. It tracked and mapped just as it's supposed to, like this one did up till a month ago, while in my pocket.

My two previous posts on this, with screen shots of the map on the phone, are here and here.

This has gotta be a problem with a GPS setting. The phone is a Moto g7.

In Fitbit Settings > Advanced Settings, Automatic location is On, and

Battery optimization is set to Not optimized (which means it does not restrict background battery).

What other GPS settings are there?

How do I keep GPS on when the screen is off?

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A separate question about posting here...

How to I answer someone replying to me without it looking like an answer to my question (with a Choose the Best Answer button)?