Connector Set Value Extension for Revit to 'fix' the ArgumentOutOfRangeException when setting Radius, Width, and Height.

ConnectorSetValueExtension.cs

using Autodesk.Revit.Attributes;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.UI.Selection;
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Linq;

namespace RevitAddin.Commands
{
    [Transaction(TransactionMode.Manual)]
    public class CommandConnectorSetValue : IExternalCommand
    {
        public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elementSet)
        {
            UIApplication uiapp = commandData.Application;

            UIDocument uidoc = uiapp.ActiveUIDocument;
            Document document = uidoc.Document;
            Selection selection = uidoc.Selection;

            var elements = selection.GetElementIds().Select(id => document.GetElement(id));

            using (Transaction transaction = new Transaction(document))
            {
                transaction.Start("Change Connector Value");
                foreach (var element in elements)
                {
                    var connectors = GetConnectors(element);
                    foreach (var connector in connectors)
                    {
                        if (connector.Shape == ConnectorProfileType.Round)
                        {
                            connector.SetRadius(connector.Radius + 0.05);
                        }
                        if (connector.Shape == ConnectorProfileType.Rectangular || connector.Shape == ConnectorProfileType.Oval)
                        {
                            connector.SetWidth(connector.Width + 0.05);
                            connector.SetHeight(connector.Height + 0.05);
                        }
                    }
                }
                transaction.Commit();
            }

            return Result.Succeeded;
        }

        private IEnumerable<Connector> GetConnectors(Element element)
        {
            ConnectorManager connectorManager = null;
            if (element is FamilyInstance familyInstance)
            {
                connectorManager = familyInstance.MEPModel.ConnectorManager;
            }
            if (element is MEPCurve mepCurve)
            {
                connectorManager = mepCurve.ConnectorManager;
            }
            if (connectorManager is not null)
            {
                return connectorManager.Connectors.OfType<Connector>();
            }
            return Enumerable.Empty<Connector>();
        }
    }

    /// <summary>
    /// ConnectorSetValueExtension
    /// </summary>
    public static class ConnectorSetValueExtension
    {
        /// <summary>
        /// Set the radius of the connector. 
        /// </summary>
        /// <param name="connector"></param>
        /// <param name="radius"></param>
        public static void SetRadius(this Connector connector, double radius)
        {
            using (new CultureInfoChanger())
            {
                connector.Radius = radius;
            }
        }

        /// <summary>
        /// Set the width of the connector. 
        /// </summary>
        /// <param name="connector"></param>
        /// <param name="width"></param>
        public static void SetWidth(this Connector connector, double width)
        {
            using (new CultureInfoChanger())
            {
                connector.Width = width;
            }
        }

        /// <summary>
        /// Set the height of the connector. 
        /// </summary>
        /// <param name="connector"></param>
        /// <param name="height"></param>
        public static void SetHeight(this Connector connector, double height)
        {
            using (new CultureInfoChanger())
            {
                connector.Height = height;
            }
        }

        /// <summary>
        /// CultureInfoChanger
        /// </summary>
        public class CultureInfoChanger : IDisposable
        {
            private readonly CultureInfo CultureInfo;

            /// <summary>
            /// CultureInfoChanger
            /// </summary>
            /// <param name="name"></param>
            public CultureInfoChanger(string name = "en")
            {
                CultureInfo = CultureInfo.CurrentCulture;
                CultureInfo.CurrentCulture = new CultureInfo(name);
            }
            /// <summary>
            /// Dispose
            /// </summary>
            public void Dispose()
            {
                CultureInfo.CurrentCulture = CultureInfo;
            }
        }
    }
}

Unable to size MEP connectors with Revit 2021 ?
https://forums.autodesk.com/t5/revit-api-forum/unable-to-size-mep-connectors-with-revit-2021/m-p/11639028/highlight/true#M68181