Summary

I loaded up the original .stl in Cura and Craftware they seemed to show that it would print solid.

I installed MatterControl and loaded it up and it looked like it would print with holes. I don't like to connect my PC to the printer for prints though so I exported the .gcode and printed it that way.

It printed with holes but didn't print the top layer so it was a bust.
I tried printing from Cura anyhow and it printed a solid slab as expected.

I imported the .stl file into tinkercad.com and ironically the only part it did render was the holes. So having the hole spacing I added a block on top and grouped it so the holes would subtract.

Now I had a workable part, so I exported it as .stl again and printed it using Cura. everything worked out great!

In the picture the oringial .stl print from cura is on the left, then the mattercontrol print of it in the middle and my remix printed with Cura is on the right. I made it a bit thicker to match the 5mm of the original part for rigidity