I am running into the same issue. It seems like the `%run` magic command is trying to parse the entire cell content as its arguments. So if you have
%run "my_notebook"
print("hello")
in the same cell, you will get the following error: `Failed to parse %run command: string matching regex '\$[\w_]+' expected but 'p' found. If notebook path contains spaces, wrap with double quotes.` But if you remove the `print("hello")`, it will run fine.
This is quite frustrating and I would assume that it's a bug.