App Engine and Cloud functions were apparently returning error rates of > 30 percent overall between 11 a.m. and 3 p.m., with some projects experiencing a 100 percent error rate. GCS was also experiencing issues for the first half, which was attributed to the networking issues. Google said the networking issues were resolved initially but then stated they were investigating the GAE issues. Those issues were resolved, and the networking issue has been reopened as of 2:35 eastern: https://status.cloud.google.com/incident/cloud-networking/19....
GAE and all other services still show green here, of course: https://status.cloud.google.com/