Troubleshooting GE/jasco three way switch

I have a chandelier that is controlled by a GE/jasco 3-way switch combo, after being on for a while, the lights dim down to being barely on. Turning it off then back on fixes the issue.

To figure out of it’s the switch or the fixture gone bad, I could take down the fixture and install a known good one and see if the problem persists, and that would be the tell. But it got me thinking, is there another way to diagnose the devices?