Query string contains repetitive parameters
This means that the URL in question contains a query string with the same parameter more than once.
Why is this important?
In a URL, the query starts with a question mark, with multiple query parameters separated by ampersands ("&"). Each parameter will change the page in a different manner, for example one parameter might be to filter and other one might be to sort. As such, each parameter should only appear once in a URL.
An example of a URL with repetitive parameters would be: https://example.com/page?filter=red&filter=red
Since the second parameter is redundant, the existence of this URL could lead to duplicate content issues, since the content would be identical to the URL https://example.com/page?filter=red
Additionally, if a URL contains repetitive parameters with differing values (e.g. one is red and the other is blue), you will have no guarantee which one the code will use (or indeed, which one should be considered 'correct'). This could also indicate a much bigger problem, as it might imply an issue with the logic of the underlying software which generates the URLs in the first place.
What does the Hint check?
This Hint will trigger for any internal URL which contains a query string which contains at least one parameter which is repeated.
Examples that trigger this Hint
The Hint would trigger for any URL with the same parameter at least twice:
Why is this Hint marked 'Potential Issue'?
This Hint is a 'Potential Issue', which means that it is unlikely to be affecting the site at the moment, but should be investigated as it could cause issues in the future.
You will need to examine the source of the URLs, to understand how they are being generated - it might simply be the case that a content writer has made a typo in a linking URL.
This would be unlikely, however, if the issue is present at any kind of scale, in which case it is much more likely that the URLs are being generated by a script or some sort of CMS error. As such, you may require developer assistance to track down the issue and resolve it - why is the URL being generated with the same key twice?