Bug ProBuilder Won't Let Me Select Multiple Edges After I Merged Two Objects

Here's a video showing what happens in case the title doesn't explain it well:

Here is the error message:

KeyNotFoundException: The given key was not present in the dictionary.
System.Collections.Generic.Dictionary`2[TKey,TValue].get_Item (TKey key) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEngine.ProBuilder.WingedEdge.GetWingedEdges (UnityEngine.ProBuilder.ProBuilderMesh mesh, System.Collections.Generic.IEnumerable`1[T] faces, System.Boolean oneWingPerFace) (at Library/PackageCache/com.unity.probuilder@4.2.3/Runtime/Core/WingedEdge.cs:353)
UnityEditor.ProBuilder.ElementGroup.GetFaceSelectionGroups (UnityEngine.ProBuilder.ProBuilderMesh mesh) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshAndElementSelection.cs:132)
UnityEditor.ProBuilder.ElementGroup.GetElementGroups (UnityEngine.ProBuilder.ProBuilderMesh mesh, System.Boolean collectCoincident) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshAndElementSelection.cs:107)
UnityEditor.ProBuilder.MeshAndElementSelection..ctor (UnityEngine.ProBuilder.ProBuilderMesh mesh, System.Boolean collectCoincidentIndices) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshAndElementSelection.cs:31)
UnityEditor.ProBuilder.PositionTool+MeshAndPositions..ctor (UnityEngine.ProBuilder.ProBuilderMesh mesh, UnityEngine.ProBuilder.PivotPoint pivot) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/PositionTool.cs:54)
UnityEditor.ProBuilder.PositionTool.GetElementSelection (UnityEngine.ProBuilder.ProBuilderMesh mesh, UnityEngine.ProBuilder.PivotPoint pivot) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/PositionTool.cs:67)
UnityEditor.ProBuilder.MeshSelection.RecalculateSelectedElementGroups () (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshSelection.cs:255)
UnityEditor.ProBuilder.MeshSelection.get_elementSelection () (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshSelection.cs:102)
UnityEditor.ProBuilder.MeshSelection.GetActiveSelectionGroup () (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshSelection.cs:567)
UnityEditor.ProBuilder.MeshSelection.GetHandlePosition () (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/MeshSelection.cs:524)
UnityEditor.ProBuilder.VertexManipulationTool.OnSceneGUI (UnityEngine.Event evt) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/VertexManipulationTool.cs:256)
UnityEditor.ProBuilder.ProBuilderEditor.OnSceneGUI (UnityEditor.SceneView sceneView) (at Library/PackageCache/com.unity.probuilder@4.2.3/Editor/EditorCore/ProBuilderEditor.cs:650)
UnityEditor.SceneView.CallOnSceneGUI () (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.SceneView.OnGUI () (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <437ba245d8404784b9fbab9b439ac908>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.HostView.Invoke (System.String methodName) (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEditor.DockArea.OldOnGUI () (at <a20a50bbfaff4193bf6ba6b262f9a71f>:0)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Action onGUIHandler, System.Boolean canAffectFocus) (at <78b213560771414e9fa6f1b95f5ad8bb>:0)
UnityEngine.GUIUtilityrocessEvent(Int32, IntPtr)

 

I'm having the exact same problem after joining two meshes. I wanted to bridge a gap between the two but it's impossible. Even double clicking a face won't select all of the faces. They initially select but return to a single selection once I release the mouse button. I can create a new mesh and select multiple edges without a problem. I'm going to have to build my meshes as one from scratch. Using Unity 2019.3.3f1 and the ProBuilder 4.2.3 package.