jupyter notebooks sometimes open in plain code editor mode

[williamstein]

This was recently reported to occur for some students in one class, and has never been reported ever before.

It looks like this:

Note that the word "Code" for the first menu. This means that the plain code editor was used to open the ipynb file, which is NOT any of the options registered to handle ipynb files, so that's really weird. Note in the menu here that "Code" is not an option:

The person reporting this also says " In most (but not all) cases, this seems to get fixed when students click the "x" in the top right corner." Clicking the x to close all frames just resets the layout to the default for that file type. This suggests somehow the correct layout isn't loaded, so cocalc is falling back to a single code editor.

Creating the Jupyter editor involves loading a new chunk the first time, so that the initial load of the main app is faster. Maybe this chunk is being blocked by a browser extension (e.g., an ad blocker) or the network.