Modern Celluloid will outgas. I just had a 2005 waterfall outgas in 2007 that would be and I have seen another that I have in the shop.
This is the second Waterfall I've seen - same pattern and make. I'll fix it up, its on my list.
It was stored well, I bought it in 2005. Makes me think that HEAT generated by a Worn belt or a buffer at the factory may also be a contributing factor.
You will notice it is scratched up, it's from using it in the shop. This is a disassembly area and it needs to be cleaned up a bit.
Here is a couple pictures.
The first picture you can see a line of.............pitting

Also discolored bolster and pins.
Second picture pins, shield, and lower bolster are tarnished. You can see the year, just click on the picture.
Third picture is the same as the first, blade is held open.
Last picture is the same as the second, just a different angle.