The reason this works is that the non-functional thrusters pass the fluid through to the central thruster, because they merge the fluid segment even though they can't consume the fluid.
The current way that fluid mixing works is slightly unintuitive, and I will be improving it in the future. But for now, this is working as intended.
Pictures don't show because you didn't link them — you linked the page instead.
The reason image storage websites (especially free ones) don't make it as easy as it could be is because by doing this everyone downloading (by looking) at that image is leeching their computing resources.
(It's still easy though, just link the image itself.)
You should rather upload the media here, where it will be kept together with the rest of your post, and will avoid these kinds of issues with lost images : https://www.matrixgames.com/forums/view ... 2#p2827272
(Also I think it makes it easier for back up crawler bots, like those of the Internet Archive ?)
Also, this shouldn't be happening even with the passthrough, you're probably instead suffering from a pipeline fluid sharing issue that you're the one to blame for : viewtopic.php?p=632632#p632632
(And one that you shouldn't ever try to solve by removing and replacing pipes.)