its C3 limitation, this issue is also with in original based 3d shape plugin i ask on forum about this:
https://www.construct.net/en/forum/construct-3/general-discussion-7/3d-boxes-3d-...
I commented in that thread with a possible solution, but I imagine it's a bit more complex than Ashley would want to implement (it would be best if it was an option, not always on.)
