Jupyter variables not loading (AST tracker error)

[Kugeleis]

I recently observe in various projects that jupyter (data wrangler?) stops working because it gets stuck in "loading variables". A reload window sometimes helps. The tendency is with increasing notebook size (not really big) the problem arises. I have no solution. The full error log entry is like
ERR [Extension Host] Document vscode-notebook-cell:/path/to/my/notebook.ipynb#W6sZmlsZQ%3D%3D not found in AST tracker

Any idea how to fix it, avoid it or nail down the root cause?