
Additional note:
This only applies to this valley area, the transition is correct(ish) at the northern and southern ends of the central pass. Where the southern valley bottom broadens in the central area the 'correct' behaviour is not carried for this central depression area.
FWIW, the valley bottom should only be at 275m according to SRTM-3 data, so perhaps eliminating the valley contour within this region would be preferable until the map classes can updated to use additional contours (automatically generated from SRTM or equivalent data?) or a raster height map.
The artefact is quite obvious in the COTA MM height map as well, as an abrupt 'pale' transition in the centre.