Repairing Imported Model

[MarkESmith]

When creating a core & cavity in within Mold design a :

Failed to join the runoff surfaces onto the base body.
Entity-entity intersections are detected within the product.

Message appears.

Exporting to fusion, repatching fillets, healing to 0.000001mm, saving as SAT, IGES, splitting & deriving - fixes some thing but breaks others.

Any suggestions, tips, workflows for fixing dodgy data?

Thanks

MES

[JDMather]

Attach the original file here.