3D modeling is broken

It appears as of posting the screen shot. 
There is no problem in 2D

In the next cube, you do not have symptoms.

when you play a cube you see it without any player additions, that’s so your trace is not biased from what others traced.

If that is not the case and you can see blue in the 2D all the way from wall to wall then the cube has a 3D meshing problem, it cannot be corrected by players but developers can remesh it.

to notify developers of a cube having mesh problems type !no3D in chat and the bot will give you a link paste cube ID, your username and cell name (example: MC228) in the respective columns.

I’ve traced a few cubes where the 3D was almost entirely missing and almost all I could see in that cube were my own tracings. It can be really fascinating, especially if you’re filling in lots of fiddly bits. Didn’t know about reporting it as a problem.

Yep, you can report it and then we can remesh (rebuild the 3D segments) so that others will have an accurate cube rendering.