Round the end of January there has been some time where created redirect source pages were not tagged as redirects, leading to redirect pages that did not redirect (ugh). One of the occurences was mentioned in the nl.wp village pump and fixed by forcing an edit. I fear there may be more in nl.wp, and that there may be more wikis with the same issues elsewhere in the Wikimedia universe.
On IRC IAlex tells me that there allegedly is a maintenance script to fix this. Please run it for nl.wikipedia, so that these inconsistencies are fixed.