For the first time ever I can now access all areas of Vault 3 without getting the DLC error. Before I could only enter the first area (Recreation Area) and if I went to either the Living Quaters or the Maintenance Wing....the autosave created from leaving either of these 2 areas back into the Reacreation Area would always become corrupt. And so would Any manual saves past that point. I tried many many times but it would always corrupt my saves.

The patch has finally fixed this issue.

Thank goodness! I have been avoiding that place like the plague. Now I can finally join the brotherhood without the DLC bug!