Fitbit doesn't work when phone's screen is locked

[Starbuck]

I have an Xperia XA and Fitbit Charge 2. When I am out on a run my route is not recorded. I have been in a long discussion with Fitbit about this and they think that the phone is turning off GPS when it is locked, indeed if the phone is unlocked it does seem to work fine... but then after a while the phone locks its own screen and no further data is recorded. I can't be running about with my phone's screen on, is there any way to have the screen off but the phone not locked, or for the GPS to continue to work even thought the screen is locked, or any other suggestions. Pleas help, this was not a problem with my old Xperia phone! 

[Uliwooly]

@Starbuck

Do you have stamina mode on?

[Starbuck]

No, it is not in stamina mode. 

Can I ask the question in a different way - would you expect GPS to still be running if the phone's screen is not lit and/or the phone is locked? 

[YoGem]

@Starbuck 'doze'  maybe killing the fitbit app. Go in settings, battery optimization, add the fitbit app as not optimized and try again. 

[Starbuck]

Thank you, that is not an setting I have ever seen before. I added Fitbit to not be optimised. I will try it out tomorrow (it is 9pm here now) and let you know if it worked. 

[Starbuck]

@YoGem 

Annoyingly this solution does not work, I really thought you had found the problem. 

I tested the Fitbit and phone twice. Once with the screen locked (did not record any location data except my start point) and once with the screen unlocked (it recorded location data for about one minute). I checked that the phone was still unlocked at the end of the second run and it was. 

Why is the phone / app not recording more than about one minute of location data? What is happening after a minute to make it stop? 

Today I will try a different app (Runkeeper) and see if it has the same issue. 

[Starbuck]

So... I used Runkeeper to track my activity today and it worked seamlessly, even with the phone locked it logged my location all the way. There is something going on with the Fitbit app and the Xperia XA as my old Xperia worked just fine with the Fitbit and the Fitbit app. 

Any suggestions on what I can try to get it to work before I return the Fitbit to store as not compatible with my phone? I'd really like to to work!