CDE Button doesnt recognise JSON.stringify() on second use

I have a CDE button component that gets some data off the page, pushes it into an array and then lastly updates a parameter with:

Dashboards.fireChange("param1", JSON.stringify(selectedPayload) );

The first time this button is used it works perfectly fine.

On interaction with the page and then a second attempt at clicking the button the button never succeeds in running its query and returns error:

Uncaught TypeError: JSON.stringify is not a function

I can't get to the bottom of why this is happening. Do i need to refresh my button component somehow? i tried creating a function and managing the JSON.stringify() part before passing into Dashboards.fireChange() but this still didn't work.

I a at a loss of what to do here. Could anybody offer some help? Or is this a bug?

Thanks!