C.A. Seydel Söhne Sampler G/D

The bottom half of the D row of my G/D sampler is remarkably out of tune, and it gets worse the lower down the scale you go - the lowest D is closer to C# than D, playing a chord on these bottom notes sounds atrocious.

Also, it's worth noting that the D is an octave above the G - I picked it up hoping to play it like a melodeon, because Seydel's own website has a tuning chart that says the D is below the G, but then it says in a footnote underneath (that I missed) that the chart is wrong.