• VSCode Version: 1.49.0-insider, commit e790b93
• OS Version: Win10 19041.450 (2004)

Steps to Reproduce:

1. Install the .NET Interactive Notebook Extension to the latest insiders build.
2. Open a blank .dib file.
3. Set the first cell to new System.Random().Next() and execute.
4. The cell executes as expected.
5. Ctrl+Z => no visible change.
6. Ctrl+Z again => cell metadata gets backed off such that it thinks it's running again, but it's not really. No new or different output is produced and the notebook's execute method isn't hit.

Does this issue occur when all extensions are disabled?: N/A

Issue first discovered in dotnet/interactive#748.