Error 431 on v2/persons

When working with persons endpoint I'm getting 431. Same calls have been made the last month without issues. The same issue appears on the api.personio.de documentation page, when trying the example code there. Chance of getting the error is about 50:50. Why is that? The only headers in the request is the access token and accept

curl --request GET  
     --url '<https://api.personio.de/v2/persons?limit=10'>  
     --header 'accept: application/json'  
     --header 'authorization: Bearer papi-*****'