The only clue that I get that there is a problem is that the mediawiki-api-error field says "failed-modify" ?

Here's my Request URL shown in the GET just before the POST :

https://www.wikidata.org/w/api.php?action=wbgetentities&format=json&ids=L14699%7CL184508

and here's the screenshot of the Response:

image.png