I am getting 2x errors with Cascading Drop-downs.
I have tried multiple variations, using the latest DFFS 21Jan2018, (I have just upgraded).
1: The ID Column does not populate drop-down. (No errors in debug or console)
2: And 3x columns similar to the format “_x0023__x0020_of_x0020_Seats_x00” shows up in DFFs NewForm.aspx with an error as attached:
The field or property ‘_x0023__x0020_of_x0020_Seats_x00’ does not exist.
I know this field exists as I copied & pasted directly from the Fields Tab of the Look up list. If I remove this column from the cascade tab, the filtering works fine, except the ID Column does not populate.
I think the error is related to to long field names. The length of the names is 32 characters, and when you exceed this limit, the field should have gotten an unique ID, but for some reason this unique ID is put as the 33 character and therefore it fails. In my tests however I cannot recreate this error so it might be related to your SP environment.
The fix is to recreate the field names using only valid English letters and underscore and no spaces. In your example: “# of seats” should have been written like “numberOfSeats” or “no_of_seats”. When you have crated the field, go back and change the name to “# of seats” and you have a nice FieldInternalName and your preferred display name.