Android 5.x has a well-known bug which results in wrong altitudes. Only few phone manufacturers corrected this bug. Even Samsung did not correct it (I had a Samsung S5).
Some navi/tracker applications have available automatic correction of WGS84 geoid altitude on the true sea level, either in the app, in the maps or as a correction file. GPS uses this to correct on the measured altitude.
Without this WGS84 correction, the uncorrected GPS altitude in central Europe is about 40m to 60m higher than the true altitude.
Question at @lubos and @tomas: Does Mapfactor do automatic WGS84 correction?
This could also explain the deviation. (510 instead of 460)
@georem - Android is doing the correction on the most of the devices. Adding the correction on already correct altitude would generate even bigger error, also only one solution is to stop using Android's API for location and implement own solution. I think this won't happen.
It is not a bug of the app but of some Android versions.
even though Android seems to be the dirty part on some devices or versions, how about implementing the altitude addition as a correction on/off feature in MFN's configuration settings? Just to make MFN damn near to perfect.
OK, a motorbike preset with an appropriate icon is still missing, but who cares....