In both shows, renaming the seasons in TVDB created duplicates.
In World War Two they took back the changes, so the seasons 1939, 1940 and 1941 just have to be removed.
In The Great War they kept the changes, so season 2014 is now season 1914, etc. This seasons should be "merged together" if that's possible. Otherwise the seasons 1914, 1915, etc. should be removed and seasons 2014, 2015, etc. should be renamed (so followers of this show won't loose their progress).
Both shows fixed to match TVDB.
Update for The Great War: They also changed it back to the original season titles. So now the season 1914 - 1919 just have to be removed.