If you see straight lines in a GPS track, check that you are allowing MapRunF to run in the background. Otherwise, when your phone screen blanks, MapRunF is not allowed to run and so no tracking occurs until you wake the phone up and then you get a straight line joining the two end points of the "sleep".
The other thing can be, that MapRunF uses the "fused location" service which allows the phone to determine locations based on GPS, known wifi network locations and cellular towers. If these settings get messed up, you can find your location jumping erratically to some fixed point on the map (an apparently "random" point).
- Check the Android/iOS settings to ensure MapRunF can run in the background
- Check re battery saver settings to might impact the GPS
- Try a run with wifi and cellular turned off
- On Android, consider using an App like "Test GPS" to reset your A-GPS settings (https://play.google.com/store/apps/details?id=com.chartcross.gpstest)
I have been using an app - GPS Connected - which locks to the satellites. This seems to have improved the tracking. Just have to remember to Unlock when finished as there is a small draw on the battery.