Transform your gpx to a breadcrumb of POI's
Convert gpx into a ov2 file (beta)
TomTom has the bad habbit to ignore (and detour) unknown tracks if it can't be mapped to an official road (like most offroad tracks). By converting a gpx track into a file of POI's (ov2), you can follow a breadcrumb of POI's and tackle this problem.
Be carefull not to use full tracks (gpx's) but only parts of it! A full track can result in 10.000+ POI's and that might be to much for your navigation device.