24mm Tilt Shift II - poor image quality

I recently bought a 24mm Tilt Shift lens, I will use this primarily for photographing skies. I wasn't really happy with the image quality, so I did some test shots with a high contrast pattern:

Shot with a 1D MK IV body, F8, low ISO on a tripod. The images are center crops.

You can clearly see the 24mm has really ugly blue-yellow halos on every edge. The 17-40mm F4 has a perfect center.

I went back to the shop to switch this lens for a new one, but it shows the exact same problem. Did I have the bad luck of getting two bad copies, or is this normal for this lens?

Before I'm accused of pixel peeping, this problem definitely shows up in real life shots. When I'm photographing white clouds against a blue sky the edges of the clouds have really ugly halos.

If anybody has the 24mm TS II I would love to see some shots with high contrast edges.