Publishing a Utility Network service with the subnetwork table present in the map causes the supportsReturnEditsResults to = 'false'.

Workaround

1. Remove the Subnetwork table and republish the Utility Network feature service. This causes the value to be set to = 'true'.
2. Re-add the Subnetwork table after accessing the feature service from the big portal.

Schritte zur Reproduzierung