Uncaught SyntaxError: Unexpected token < in JSON at position 4

I have an AEM 6.4 project that works fine in the local environment, but on deployment to the enterprise AEM 6.4 environment, I can no longer delete components in a page, or even move them, images used in components do not show up in dialog and so on.

I see the following errors in the browser console:

I am clueless as to why this could be happening.

Any help on this would be great to move forward.