Hi Lars - those gaps are at a small size, I think smaller than the tolerance of 0.001 . Generally stuff in MoI is constructed to fit to a tolerance of 0.001 units, so it is not unusual to see gaps between things around that level of size.

If you select those pieces and use Join on them, they should join together and get a single common edge, which will in effect seal that gap.

If you need more accuracy on the construction of that piece, you will probably need to scale things up somewhat in size so that 0.001 units is an acceptable gap size.

But that blend should actually work to fill the hole if you join it with the other surface.

- Michael