Its a known bug that the Devs only recently figured out what the issue was, so they will be fixing it soon
Sorry, but this is a different bug. The Molecular Fabricator is simply missing the following tag in the ImprovementDefs.xml:
<Preclusions>
<Improvement>MolecularFabricatorc</Improvement>
<Improvement>IndustrialReplicator</Improvement>
</Preclusions>