Before you select Render To Texture, you need to remember that the door will open. There for you need to do this process in to step. First select all that are stationary. Right-click and select Hide Unselected. Now select all object that do not have shiny or metal-material. Select Render to Texture, and Render.
Next you select all, right-click, select Unhide All. Then Hide Selected. Now you have only parts that can rotate. Do the same. Select only parts that are not shiny or metal, and select Render To Texture, and Render