Greyscale bug

Have you tried reloading the web page?

Of course. even cleared cache

Same issue. Clicking grayscale makes the entire plugin unusable.

I cannot reply that issue. It works fine for my site.
Could it be a plugin incompatibility?

I can confirm as well. Completely new build and even disabled every plugin on the site – it’s not a compatibility issue.

You can view it here https://caritassalford.org.uk/
Chrome & Firefox only. Safari is absolutely fine.