Element.faces error

I need to extract all the faces of every floor within a project. However, some floors are throwing back an error as below. Does anyone know what causes this error?

The circled red area circled above is the area that I found that causes the error. The first picture below shows the floor in the state that will throw back the error. The 2nd picture is after switching the join order with another floor which resolves the error and returns all the faces. As I’m wanting to run this on complete models and won’t have the scope to be playing with individual floors to make sure their faces are being returned, I would really like to know what causes this error so I can try to avoid it.

I have the same problem. Did you find the solution?