[GRO] When you save a Sim/Household with Milestones do they then duplicate?

When you save a Sim/Household with Milestones do they then duplicate?

I saved a household and then played then in a new save file, and started getting duplicate milestones for everything X / Why does this happen?

And I do not know if it is related Sims on one side of a relationship missing all the romance social milestones.