Having an issue where I'm trying to hollow a helmet but it does not seem to hollow properly

Even when the wall thickness is less than 0.4mm it still does not seem to hollow throughout the model as shown in the image. You can see a lot of anomalies (random Polygons) as well as very little gap between the walls. (Wall thickness is 0.2 to show point)

If the helmet is cut into many pieces it is then able to be hollowed properly

When I use a different slicer it is hollowing throughout the entire model

Anybody know why or if this is a bug issue?