3D effects Bug

Hello

English is not my first language, so if I cannot express the matter properly, please feel free to ask... Features in my software are German, so maybe some translations are not exactly what they are named in English...

The issue:

I want to distort objects to isometric perspective. I want NO embossed lines, no material, no pixelation. Therefore, I apply the effect 3D rotate (classic).

When doing, Illustrator creates a clipping mask, so that some parts of the object are not visible. I can't edit this clipping mask without expanding appearance. This leaves me with not being able to edit the undistorted object. Expanding appearance is a workaround but not suitable. 

This problem occurs with every kind of object (image, text, vector graphics).  THis method worked before, so what happende here and how can I fix this?
Using 3D and Materials is not an option since this rasterizes the object and affects the colours