Dear Martina,
Thank you very much for raising the issue. We did investigate it and we can confirm that the WDQMS station schedule update for DWD on the 8th was caught in the middle of OSCAR/Surface new release. WDQMS is uploading the DWD 00 UTC file much earlier than the other Centres. That is why you only see the grey dots on the DWD 00 UTC map. The grey dots on DWD daily aggregation are coming from the 00UTC. We are currently working to fix this issue so that it doesn't happen again.
Regards,
Cristina