Just my opinion...
As mentioned by the op, I believe that what happens is if you are scrolling with your mouse wheel to move down the system page, if you accidently hover over the tuner reference pitch it will change it without you realizing.
I understand that this is what its supposed to do. However its very easy to do it inadvertently.
This can happen with any other parameter. Its just that the tuner reference moving slightly will have a greater effect than say the attack in the compressor.
A lock feature should help.
Another option could be that you would have to click on it first, before you can scroll up and down.
Peace