Steps to reproduce (facing North):

/summon Painting ~ ~2 ~1 {Motive:"Kebab",TileX:~,TileY:~2,TileZ:~1,Direction:0}

Result:
Based on the relative Y coordinate, the painting should be placed 2 blocks above command block, instead it gets placed 1 block above. This same bug also occurs by using an absolute Y coordinate, instead of a relative coordinate.

Using the same command to summon an Item Frame, works properly

/summon ItemFrame ~ ~2 ~1 {TileX:~,TileY:~2,TileZ:~1,Direction:0}