DFox hasn't changed anything since his version 1.17.1, he always uses the same signature. The problems occur when a different signed version is used before or later. Then these install-over-problems with the DFox-version. The solution would be a new clean reinstall with the DFox-version. Map(s) download is not the problem, if TT update the maps, you must also download the complete map(s). But you lose all of your saved routes, if you made a new clean install. Only that's why i made this testkey-signed version of the DFox-APK.