You guys do realize they make calibration solutions to check whether your pH meter is reading correctly... yes?
LOL, this is exactly what came to my mind as well. It's pretty easy to check the accuracy of your pH meter in a way that doesn't involve buying a second one. That said, I'm admittedly throwing stones from a glass house because there's a lot of brewing equipment that I have two of. Or six.
This would be a good time to remind brewers that calibration solutions do go bad. They absorb atmospheric gasses, as any liquid does. This changes how well they match their labeled calibration pH. If you think your probe is going bad, consider how old your solutions are as part of the troubleshooting. And use fresh, new solutions to get that "second opinion" if you think your probe is iffy.