Based on what i'm getting on how this works, it may not be possible to fix easily (i assume this uses virtual barrels and the assembling machine barreling recipes, which Barreling Machine (https://mods.factorio.com/mod/barreling-machine) moves to a custom 1x1 machine) but if you have barreling machine active and try to place a Unipipe it immediately triggers an unrecoverable error. I suppose a compatibility mode where if that mod is active it snags the recipes from there instead would work, though i'm not sure, and also not sure i expect a patch since why use barrels when you can teleport fluids, but it would be nice as this mod is definitely a bit cheaty with Space Exploration even if very nice for annoying fluid situations lol.

Together with the mod Automatic Barreling/Unbarreling Machines. Falling while trying to place a Unipipe on the surface.

Error while running event Unipipe::on_built_entity (ID 6)
Passed index is out of range.
stack traceback:
    [C]: in function 'get_fluid_system_id'
    __Unipipe__/scripts/unipipe.lua:68: in function 'onBuiltPipe'
    __Unipipe__/scripts/unipipe.lua:32: in function 'onBuiltEntity'
    __Unipipe__/scripts/main.lua:6: in function <__Unipipe__/scripts/main.lua:3>

It also creates incorrect recipes when used with the mod Beltbox Barreling.
It seems that any mods related to packaging liquids in barrels create incorrect recipes or cause errors.