Parts of model cut out during slicing  

Bad model

I would assume that the model has problems with the face orientation. You would have to check and fix this with an editor like Blender or Fusion360.

Possible STL problems, upload zipped 3MF project file

Save your current  3MF project file, zip it up, and attach it to a reply here so we can see your part & settings and give better recommendations. This sort of problem is usually related to faults in the STL that make slicing difficult. You might try running a repair on the STL.

3MF file

Groose file

I'm not really sure if this will work i'm quite new to 3d printing and using the forums.

Be sure to zip & attach

Posted by: @andrewkoubler

Groose file

I'm not really sure if this will work i'm quite new to 3d printing and using the forums.

Be sure to zip the file. Use the Attach file button right below the edit area.

title here

My PS is not liking that .3mf file.  It looks to me like it's a 'runt', missing most of the model information.

RE: Ah there it is!

Good grief, the new forum "improvements" make it so attachments and links don't stand out at all. 

I'm also getting a "model failed" error.