Before reporting:

looked for "tank", nothing about the tank came up.

Description of the issue:

When i'm building a tank, there is some manner of rendering bug when it is placed on a ring of stairs/slabs with a hole in the middle. The tank does not fully render, with some sections being invisible/seethrough.

Crashlog:

regular
minimal instance (Forge+IE)

I am unable to replicate this, and have absolutely no idea how this can happen. Can you try updating Forge to the latest build and see if that fixes it? Are you using any nonstandard graphics settings in Forge or MC?

Closed due to lack of response