By default the Trailforks map updates your blue dot location every few seconds when the app is in the foreground and the phone screen is on. If you navigate to another page in the app, switch to another app or turn off your phone screen this auto location updating should stop.
You can change the frequency of this location updating in the settings or disable it by choosing the "Manual" option, so the location will only be fetched when you press the circle locate me button on the map.
This setting is separate from recording your ride, when recording your ride your GPS will be fetching locations constantly and this setting is ignored.
If your phone has bad GPS reception, or you are getting error code 408 messages, it might be a good idea to try setting the gps update interval to "Manual".
For proper use of the Trailforks app and gps location, you want to make sure your location services is enabled on your phone and you're not using a power savings mode.