Category:Pages using duplicate arguments in template calls

This tracking category is fed automatically by MediaWiki (see Special:TrackingCategories). It lists pages using templates and passing them multiple parameters under the same parameter name.

Except these rare cases of black magic (internal to complex templates), this is most often a simple editing error when using templates in the listed pages. They are simple to resolve from the Wiki editor: edit the page and preview it ; MediaWiki will show error messages at top of the preview specifying the template name and the overwritten/conflicting parameter name ; only the last occurence of the template parameter name is used.

In complex cases to discover what is being reported as a problem you can use binary search: clear sandbox, copy half of page into sandbox and check is it reported

it is reported? Great! We reduced search space by half, now search in remaining part (take half of it into sandbox)
is sandbox not reported? Great! Then the other half has a problem!

In some cases, these are only dummy parameter values assigned to the same dummy parameter name (the last assigned parameter value, in syntax order, is taken into account and overwrites any previously assigned value). Some old-fashioned templates are using some kind of black magic by first passing them a series of static parameters, and then overwriting some of them using varying parameter names, but MediaWiki does not like this method and signals these overwritten parameters.

Unfortunately, MediaWiki still does not have a stable way to indicate that the parameter is dummy and will be ignored by the template implementation (such as a stable parameter name, including the empty parameter name different from positional parameters which are implicitly numbered). So many pages are reported in this (hidden) category (solving these errors requires an excellent knowledge and understanding on how templates work in MediaWiki).