I would like to get a part of a city model from .dwg into cesium. I have converted the model into 3dtiles but after uploading it into cesium, a problem with rendering all surfaces has come up (check attached image). As I rotate around the model only some of the surfaces are visible, while they change while moving around. This means that they are actually there but not always visible?! Checking back the initial model, it seems fine (2nd attached image). I followed the same process with a different model and it worked perfectly. I am using Cesium 1.49 in windows10. The convertion was done with fme from .3ds to citygml. Any ideas what is the cause of this issue? I would appreciate any kind of feedback!