Rocket Validator looks for accesibility violations on your pages using the axe-core accessibility engine, hosted on our own servers and integrated into our web crawler. You don't need to buy an additional license, everything's already included in your Pro account at Rocket Validator.
A11Y check: accesskey attribute value must be unique
Accessibility rule: All accesskey attribute values in a document must be unique. Put another way, accesskeys must not be repeated to prevent unexpected effects for keyboard users.