This one had, too. There was a rainbow-like colouring on it and the silver had just worn off from places. Luckily someone on this forum told me that Lasershop in Germany makes new replacement mirrors. Bought one for about 15 euros including freight and installed it. Now everything is clear.
The focusing helicoid feels a bit stiff-ish even after greasing it, and the magnifier loupe pops up a bit too high, I have to push it down a bit to focus it properly with the ground glass. Other than that, it's a great little camera.