I am experiencing a similar issue when copying sheet inside workbook (or adding by a copy).
When I edit a cell in the new or old sheet, the same cell in the other sheet is also edited.
I have tried to set OutlineLevel = 0 on every column and row, but to no effect.
package.Workbook.Worksheets.Add("Data " + sI, ws);
ws.Column(3).OutlineLevel = 0;
ws.Row(11).OutlineLevel = 0;
I have even tried to set OutlineLevel before and after the copy and on the new and old sheet.
It seems to me like it should be a property on the sheet level, as I can remove the grouping in Excel on the tab/sheet by right clicking.
What am I doing wrong guys?