Triggering pipeline through API doesn't work since update to version 9.5

We have a self-hosted CE edition and updated to 9.5 this morning. Now the API trigger for pipelines doesn't work anymore.

The URL used to be curl -X POST -F token=TOKEN -F ref=REF_NAME https://gitlab.example.com/api/v3/projects/125/trigger/builds

That results in the error {"message":{"base":["Insufficient permissions to create a new pipeline"]}}

Now we changed that to curl -X POST -F token=TOKEN -F ref=REF_NAME https://gitlab.example.com/api/v4/projects/125/trigger/pipeline

This gives us the error {"message":"500 Internal Server Error"}

Not sure where I could find more details about the error. Can you please help us?