Factorio: 0.17.68
Krastorio: 1.4.23
Fluid Must Flow: 1.0.2

Not sure this is a Krastorio problem, Factorio problem, or Fluid must flow, but when you place blueprints with connected steel pipes and outlets or outlets connected to duct pipes, they often do not "connect" and have to be decontructed/reconstructed to snap.

Nevermind. Saw the second Fluid Most Flow check box and unticked it (one for snapping to smaller pipes). Immediately fixed the problem. Probably not something to toggle in a big already complete base.

I'm sorry, in this days I'm really occupetad on Krastorio, I will look better this problem anyway when I got time, Thank u for ur report.

Take your time. Quick update: I noticed this ocurring quite often with underground duct to outlet connections. I had to deconstruct and reconstruct them. It may be unrelated, but in order to get my connections to work I had to make sure the underground ducts were not next to other underground ducts.

I analyzed this bug, u should guess that the Factorio engine must have a predictable behaviour, if isn't the problem should not of the mod but of the engine, how can I adjust the fluid boxes if the game give me different behaviour when the clock of my PC change?

If this problem continue to exist I think that u should report this to the Factorio dev team