Might it be from a reaction to glue or paint?On the bands around the steam and sand dome I used O-rings and in this picture you can see on the steam dome that it has come apart and is laying down on one end. Not sure why but the crack after a while, and I replaced them not to long ago and they are cracking again. Never out in the sun just heat. Might have to find something else.
Might it be from a reaction to glue or paint?
And another totally different possibility - are the o-rings rubber? Are they in the same room as or a room close to one of those ionizing air filter/purifiers? In 1990s one I had destroyed everything rubber in same or adjacent rooms, HO locomotive traction tires, jacket wrist elastics, chair cushions, and a couple other things.