My 6 year old Cam5 laser has mirror issues. I bought an alignment tool online and it works great (other than the short battery life).
What is has demonstrated is that my #1 mirror has lost a considerable amount of reflectivity. After thoroughly cleaning it, the beam from the reverse alignment tool is significantly diminished in both beam quality and intensity.
So I bought new mirrors. No big deal right?
Well, after removing the #1 mirror, I learned that the threaded piece that secures it to the holder is glued to the mirror. I have tried, using a razor, to separate the two. I ended up breaking the mirror.
Before I go any further, I thought I’d ask the forum for suggestions.
Rule of thumb: When brute force isn’t working for you, you’re not using enough of it. 
Given that you have a replacement in hand, chisel the fragments off the lock ring, clean the ring and the mirror mount with whatever solvent dissolves the gunk (alcohol / naptha / acetone), then reassemble in reverse order.
If the mirrors have been working undisturbed for six years, they’re probably all glommed in place with condensed fumes and gunk. Replace all of them just to be sure.
Plus, assuming you haven’t done so already, check the focus lens, because it’s likely in worse condition.
I was sure you could buy the mirror rings, but I can’t seem to find them. You may be stuck with using the @ednisley method.
it’s nice to be able to buy that without having to purchase the whole assembly.
Good luck
You were correct.
The mirror had become stuck to the ring and I had to use a chisel. Mirrors were definitely in bad shape. They looked good but the reflection from the alignment device is now crystal clear. Combined with the dot from the SPT tube, I don’t think, no, I’m sure! I have ever had the beam so tight.
Brute force: 1
Gunk: 0
My machine came with molybdenum mirrors that trade a percent of reflectivity for being nearly indestructable. From what I’ve read, as long as you don’t clean them with a Brillo pad they’re easy to live with.
If yours get extra cruddy again, try moly mirrors.