Cura filling in holes

[bdobles 0]

I am a public library librarian running CURA 2.4 with an Ultimaker 2+ printer with no issues for a year not. But today, one of our patrons submitted a file that shows it should be printing with voids or holes in the design through which screws are supposed to fit. In CURA, it looks fine, but it prints with those holes filled in. A search of the forum suggests I navigate to Mesh Fixes in custom settings and choose "Type A". I went to Preferences and set it up so I could see the Mesh Fixes options but there is no "Type A". There is a choice for "Remove All Holes" but it is already unchecked. I would appreciate any help and advice. Thanks!

[gr5 2,167]

First of all don't get the "visibility" check boxes confused with the actual settings. That gets me often.

Look at the part in cura xray view. If there are any red areas the cad model needs to be fixed. I'm guessing they made it in sketchup. If so then have the designer read this fantastic article:

https://i.materialise.com/blog/3d-printing-with-sketchup/