D15E2 - PdC/Nord (sic) is off where OSM has put the border. Check you have it in right place.
General note on departement borders - not region borders - all over France:
I located them where the administration / maintenance changes. That means where a mile post (or stone) can be found on GSV or between the blue "departement welcome signs" if they exist. Where I can find a pavement change or where a marking is on the road. Often Dxx extends a little bit to the next junction in the neighboring departement.
My point wasn't that it was in the wrong place, my point was that it
might be in the wrong place and that it ought to be checked. Given I'm not seeing any points that are off for junctions and the like, I'll ignore when a border point (as opposed to a junction point with a road just beyond the border, which I was ignoring) doesn't match where OSM has put the border.
D40, D40E1, D42, D42E3, D42E4, D43, D44, D44E1, D44E2, D45, D46, D46E, D47, D48, D49, D49E1, D49E2, D49E3, D49E4, D49E5 - all the 40s are fine!
D50 - fine
D50E1 - D50/D50E2 -> D50 as, IIRC, in IDF, you collapsed intersections where a route met a parent and a suffixed route to just mention the parent.
D50E2 - D50/D50E1 -> D50 as ditto. See also points like D40_W on D46, which also intersects with D40E1. Or D80_S on D59.
D51 - D937 -> D58/D937
D51E1, D52, D52E2, D53, D54, D54E1, D54E2, D55, D55E1, D55E2, D56 - fine
D57
- D301 -> D301/D941
- D937 -> D58/D937
D57E1, D57E2, D57E3, D58
D58E1 - D58/D58E4 -> D58
D58E2, D58E3 - fine
D58E4 - D58/D58E1 -> D58
D59, D59E2 - fine