Pictures would be great. But, I think you need 10 posts before you can upload. In the mean time, are the gaps consistent? are they always on the same side of the joint? If you set up your dado set for a specific width of cut and run a scrap board through, is the resulting dado exactly what you set up?
The dado set may be wobbling, for one of many reasons.
If you followed the assembly instructions and the video of the process, it's almost automatic.
The Patriot Woodworker
'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton