Steps to Reproduce:

1. Open any article, click on 'Edit source'.
2. In 'Edit source' mode click on 'Syntax highlighting' -
   
   - no edits/actions are needed, the option selection will be automatically remembered.
3. Go to SE article and click on 'Edit source' - the guidance panel link "Switch to the visual editor" won't work. Un-select 'Syntax highlighting' - the link will load VE (sometime it requires to reload the page).

Note: Step 2 is not quite required. Enabling/ disabling 'Syntax highlighting' option on one of the SE article will display the issue - sometime it requires to reload the page after selecting/un-selecting 'Syntax highlighting' option.