PVC solar 2" pipe joints degrading from ultraviolet...something I should anticipate more of?
PVC (plumbing) is not rated for sunlight exposure and needs to be painted or otherwise shielded from sunlight.

PVC (electrical) is not rated for plumbing/pressure use, but is UV resistant.

So, if you have unprotected PVC pipe in the sun, expect more problems. And paint it, though already-damaged sections may still fail after painting due to existing damage. Paint should be applied after assembly, including couplers/joints.