Between 15:02 and 15:12 UTC 3480 requests to rrdp.ripe.net resulted in a HTTP 404 response. As a result, some Relying Party instances (validators) may have fallen back to the rsync repository.
Due to an unknown cause, a load balancer intermittently directed traffic to a fallback instance. This resulted in a mismatch between the content of the notification.xml file and the other RRDP content (notification and update files) that was available.
We are doing a deeper investigation into the root cause of this situation.