We also had this same problem with mixing of these fluids in a fluid system connected to an EM plant. Ours involved a single pipe between two EM plants, which should have been electrolyte but occasionally became holmium solution. The electrolyte system usually had 0 total electrolyte in it; I assume ...

It's possible to have a belt pointing one way, but when you blueprint it it's orientation is different.
Steps to reproduce:

Build a setup like this:

[attachment=2]initial configuration.png[/attachment]

Now drag a ghost belt downward across the entire thing:

[attachment=1]ghost build.png ...