this happened while i was looking at my RBMK and the servo part of the auto control rod has dissapered and in older times i also had the cover dissapere and the normal control rod servo also a wierd bug where the shadows get stuck

lso

The shadow thing is a general issue that sometimes happens with connected texture blocks when loading a chunk, I don't know why that happens. The caps on the RBMK disappearing is in most likelyhood a vanilla bug since for those tile entities the renderer never even runs to begin with, so it's not actually a bug with the cap rendering. I doubt I can fix that one.