Hi @BramKn I am so sorry for the trouble. This appears to be a problem introduced with user management - it seems error workflows can’t be executed by all users.
Following another report, @krynble has worked on a fix (refactor: Change permission check to be based on workflow settings by krynble · Pull Request #5390 · n8n-io/n8n · GitHub) essentially allowing an error workflow to be executed depending on the “This workflow can be called by:” setting of the workflow.
This is currently awaiting a review and should hopefully be available soon.