Off-line issue meaning map reload is a must fix issue.
Huge design flaw of turning device off / logging off the app deleting all the map data you downloaded.
Makes the app totally useless if you downloaded maps in area of signal in readiness for a trip in an area with no mobile signal e.g. (with my mobile provider) big swathes of N. Yorkshire, Scotland.
A hint to OS, if you are wild camping for a few days, so no chance to phone recharge, a lot of that time your phone will be off (conserve battery), phone (and a battery munching GPS app) will only be switched on sometimes.
Obv proper walkers have paper maps, but such an app could be useful on occasion (even something as simple as checking you are where you think you are based on map / compass nav when mist / fog has descended), but not when each time you turn your phone on it has lost your downloaded data.