The underlying function used for calculating Latitude and Longitude -also used in other places inside the radiosonde app- was returning a positive value always.
But it needs to cope with negative values also (i.e. Lat and Lon)
Fixed by just changing the returning value into int32_t (even if the calculation is done in uint32_t, the actual sign is passed thru when returning the calculated value -those are the same 4 bytes, interpreted either as (before) unsigned or (now) signed)