On this page created by users for testing, there are two links to the German Wiktionary. This is not a bug, nothing that should be solved by the developers: this is something that could happen if one of the Wiktionary versions has two pages with a very similar title (here, bleu... with the two possible characters for ...)
This has to be solved by the communities, to improve their pages and harmonize the way they write the words and use the characters.
Then, they would need to find all these "multiple links" cases in order to solve them. Or not, as they decide.
This could be a special page listing all the pages that have more than one link linking to one other language (for example, 2x German).