No idea which side causes an issue so here is the same issue on py's side https://github.com/pyanodon/pybugreports/issues/254. Either way, when using the Pyanodon mods https://mods.factorio.com/user/pyanodon, waterways can't be placed on water.
No idea which side causes an issue so here is the same issue on py's side pyanodon/pybugreports#254.
Either way, when using the Pyanodon mods https://mods.factorio.com/user/pyanodon, waterways can't be placed on water.