'Another process has added the 'ContractBillingSchedule' record. Your changes will be lost.'

I am attempting to create a Project for a Business Account programmatically.

	public class ExtendProjects_BusinessAccountMaint_Extension : PXGraphExtension<BusinessAccountMaint>
    {
		public PXAction<BAccount> CreateServicesProjectAction;
        [PXMassAction]
        [PXButton(CommitChanges = true, Category = "Record Creation")]
        [PXUIField(DisplayName = "Create 'Services' Project")]
        protected virtual void createServicesProjectAction()
        {
            BAccount bAccount = Base.BAccount.Current;
            if (bAccount is null) return;

            PXLongOperation.StartOperation(Base, delegate ()
            {                
                CreateServicesProject(bAccount.BAccountID);
            });
        }

        public static void CreateServicesProject(int? bAccountID)
        {
            if (bAccountID is null) return;

            var bAccountGraph = PXGraph.CreateInstance<BusinessAccountMaint>();
            BAccount bAccount = bAccountGraph.BAccount.Current = bAccountGraph.BAccount.Search<BAccount.bAccountID>(bAccountID);
            if (bAccount is null) return;

            var templateGraph = PXGraph.CreateInstance<PX.Objects.PM.TemplateMaint>();
            PMProject template = templateGraph.Project.Search<PMProject.contractCD>("SERVICES");
            if (template is null)
                throw new PXException("A 'Services' template does not exist.");

            PMProject servicesProj = SelectFrom<PMProject>.Where<PMProject.customerID.IsEqual<@P.AsInt>.And<PMProject.templateID.IsEqual<@P.AsInt>>>.View.ReadOnly.SelectWindowed(new PXGraph(), 0, 1, bAccount.BAccountID, template.ContractID);
            if (servicesProj is null)
            {
                var projectGraph = PXGraph.CreateInstance<ProjectEntry>();
                PMProject project = projectGraph.Project.Current = projectGraph.Project.Insert(new PMProject());
                projectGraph.Project.SetValueExt<PMProject.customerID>(project, bAccount.BAccountID);
                projectGraph.Project.SetValueExt<PMProject.templateID>(project, template.ContractID);
                projectGraph.Project.SetValueExt<PMProject.description>(project, "Services");
                projectGraph.Project.Update(project);

                projectGraph.Save.Press();
            }
        }
	}

Sometimes it succeeds, but for some accounts, it fails repeatedly with 'Another process has added the 'ContractBillingSchedule' record. Your changes will be lost.'

Is this code-related or a bug? I did see a few other posts of similar errors in some versions of 21 R1, but we’re in 21 R2.