The error pops up on the start of the game when trying to load Fluid and Squeak Through.

"Failed to load mods: Error while loading entity prototype "duct-underground" (pipe-to-ground): invalid pipe connections specification for offset (.5676562500, -1.5976562500). The offset must be outside of the entity bounding-box."

I tried looking though the files to find where this code resides, but no avail.

I will fix it later

FluidMustFlow (1.05)
PickerTweaks (2.1.0)

Enabling "Smaller Collision Boxes" in PickerTweaks causes the same issue. It's the same mechanic as Squeak Through.

I have to write to PickerTweaks author, will see

Did you get a response from the PickerTweaks author yet?

No I had some work on K2, but I will do it soon