We are still developing Print Check and we know it still does some unexpected things.
We've put together a list of known issues and some ideas and how you can work around them:
Issue: The cone shape does weird things.
Why does it do that?
If the base of your cone is exactly lined up with the face of another shape, Print Check struggles to join them.
What can you do?
Try moving your cone so the base slightly overlaps into the shape it is sitting on. This will help Print Check know that they are supposed to be joined.
Try using a different shape in your design if possible.