I have an Omega D2 and DII. I've been noticing, if I burn in my prints to some significant degree, parts that did not (intentionally) get exposed during this burning process gains some density. Obviously, stray light is exposing the covered part.

On my D2 and I'm pretty sure everybody's D2 has the same problem. Mine is in very good shape with no obvious damage.

There are some significant light leaking from where condenser meets the neg carrier. Also, there are some leaks from the lamp housing going straight up. I can tell this because there is a shape of vent holes projected on my ceiling.

My walls are white except the part directly behind my enlarger. That part has black paper pasted on it.

This is a very common enlarger with a long history of extensive usage by professionals. Are there common modifications or treatments done to this enlarger to prevent stray light exposing paper? I'm looking for "best practices" with this gear. Can anyone help me?