There might be a couple of things to check here.
1. You can try reinstalling Enscape (I doubt this will work but good to rule out).
2. Check that all your Drivers are up to date, especially your graphics card drivers.
3. Have a look whether there are some problem elements. The kinds of things you are looking for are;
- Degenerative coordinates on elements, which are overlapping points, causing faces not being created. This is most common in objects, Meshes and Morphs. If you show all, open 3D window and then open the Archicad Report, it will list elements that might have these issues.
- High Polygon count. If you have graphisoft's goodies suite installed, you can open the 3D window and use the polycount tool to check how many elements and polygons you have. Ideally you want to keep this count below 5,000,000 polygons.
- Complicated imported elements. Imported IFC elements can sometimes be corrupted. Imported RFA, SKP, 3DS can be over complicated geometry, depending on how much detail they were modelled in.
- You can try an Open & Repair. Start Archicad > click Open > navigate to the file and select > tick the option "Open & Repair selected file > Click Open.
You should also reach out to Enscape and ask them for assistance.