The issue may be caused by the following problem: When I have a linked production block, I cannot (AFAIK) control, which ressources are trying to match the required amounts. So a build that should only create the purified water for itself instead tries to produces enough for all higher up production blocks.
The reverse also happens, where I want a build to output more then one ressource matched to the required output, but it doesnt regard those as outputs. (like when you need iron ore and iron plates in upper builds, but it only counts the iron plates, except much more complicated because of seablock)
This wold turn this more into a feature request. I could not reproduce the issue with an unlinked production block.