Can Framelines that have faded be restored?

[NicholasNicholas]

I have a VI-L with near invisible frame lines. The viewfinder is somewhat foggy. It's a shame as it's a beautiful camera otherwise.
I pulled the top plate off and gently cleaned things on the surface... the finder set to 50mm is very foggy, and the framelines are there... but very faint and not visible when shooting.
Any way to correct this?

 

[Zuiko-logist]

Did it improve with cleaning?

 

[NicholasNicholas]

Did it improve with cleaning?

Not really, maybe slightly clearer the view. I didn't deep clean and pull all the prisms apart. I'm concerned I'll damage them with cleaning, or if it's not possible to come back from haze / faded prisms?

 

[Rob-F]

I think it's caused by deterioration of the silvering on a mirror or prism (not sure which). Some of the techs can restore that, it it is in fact the reason. Youxin Ye (YYE) and Don Goldberg (DAG) come to mind.