Creating private channel not working in version 5.13

Describe the bug
Creating Private Team Channel not working in version 5.13

To Reproduce
Working Code from 5.12

privateChannel.OdataType = "#Microsoft.Graph.channel";
            privateChannel.Members = new();
            foreach (var owner in owners)
            {
                privateChannel.Members.Add(
                    new ConversationMember()
                    {
                        Roles = new List<string>() { "owner" },
                        OdataType = "#microsoft.graph.aadUserConversationMember",
                        AdditionalData = new Dictionary<string, object>
                        {
                            {
                                "user@odata.bind",
                                $"{this.graph.RequestAdapter.BaseUrl}/users('{owner}')"
                            },
                        }
                    }
                );
            }

            await privateChannelPolicy.ExecuteAsync(
                () => this.graph.Teams[group.Id].Channels.PostAsync(privateChannel)
            );

Not working anymore in Version 5.13

Response:
{"code":"BadRequest","message":"CreateChannel_Private: Cannot create private channel, no members specified when calling from an Application."}

Can't see any changes to docu if there was a wanted change to the behavior to this.

Start with the provided private-channel creation call through graph.Teams[group.Id].Channels.PostAsync and compare its behavior between SDK versions 5.12 and 5.13. Reproduce the BadRequest response with the shown member construction, then trace the request serialization or API contract change; done means identifying the regression or documenting the required behavior and validating it against the reproduction.