Adventurer 3 filling holes in design!

[David1996]

hello, relatively new to 3d printing although i did some at university. I am currently trying to print a speaker grill for my car, however all the holes in the front are being filled when it gets too slicing, prior to that the design seems fine. No holes to my knowledge. Is this a setting issue or a design issue? will attach files! thanks in advance.

[Bikeracer2020]

Loaded your STL into Orca slicer and it appears you have two STL's one on top of the other.