Stacked nodes travel different paths

Hi! I’m trying to put a couple of nodes on top of each other in a variable font to solve some geometry problems. The idea is that they keep the same coordinate in some masters, and I would expect them to keep the same coordinate between those masters. But seems like they travel 1 unit apart. Is this solvable?

On this screenshot, red and orange are masters with the overlapping nodes, and blue is an instance between them:

What are those nodes do on the other axes?

Here is my current setup. As you can see, I’m trying to interpolate from vertical terminals in narrow masters to angled in normal and wide. The nodes “hide” in the four masters on the right. But any instance between them gives that one unit difference.
That seems to only happen in the exported file. If I interpolate an instance in layers in Glyphs, nodes remain correctly overlapped.

The problem also doesn’t appear in OTF/TTF formats!