Excel 97 / VBA: Minimal distance between shape nodes ?

I am creating some Shapes as even Visio 2000 does not have them.

I seem to have stumbled over a bug ..er.. feature which I do not find a reference in whole (accessible) internet: If the distance between the nodes is below approx. 8 points the VBA is soured to the point an Excel restart is needed.

Here my questions:

a) Did you ever encounter this ?

b) Please test the following code on your machine:
- Make sure no open _work_ is left unsaved
- Please run my sub first with a=8
- Paste the string here containing the version/OS as written into the active cell
- Re-run macros with diminishing values for 'a' until you get an application error
- Try with the last 'a', in my case it will not work, I need a restart of Excel, merely resetting is not sufficient

Sub MinimalNodeDistance()
 
  Const a As Single = 8 'will crash if < 8, 'souring' VBA. Excel _restart_ is required
  Const x0 As Single = 50
  Const y0 As Single = 50
  Dim sWhere As String
 
  With Application
     ActiveCell = "Excel " & .Version & " (Build " & .Build & "),  running on " & .OperatingSystem
  End With
 
  With ActiveSheet.Shapes.BuildFreeform(msoEditingCorner, x0, y0)
    .AddNodes msoSegmentLine, msoEditingAuto, x0 + a, y0
    .AddNodes msoSegmentLine, msoEditingAuto, x0 + a, y0 + a
   
    .AddNodes msoSegmentLine, msoEditingAuto, x0 + 2 * a, y0 + a
    .AddNodes msoSegmentLine, msoEditingAuto, x0 + 2 * a, y0 + 2 * a
   
    .AddNodes msoSegmentLine, msoEditingAuto, x0 + 3 * a, y0 + 2 * a
    .ConvertToShape.Select
  End With
 End Sub