Uknown warning for creating floors from curves

I’m currently getting the warning:

Warning: Floor.ByOutlineTypeAndLevel operation failed.
Curve join produced more than one WIRE in Polycurve.

I have no idea what this means, can anyone clarify? I am testing out Flux and using polycurves generated in GH to create floor outlines. The outlines show up fine in the Dynamo preview. The node is procuding nulls, although I’m not sure why.