Script Editor Issue in 8.1.18

We upgraded our servers and dev systems to 8.1.18 last week. Working in the Script Editor in the Designer, I’ve seen one project script file that, when opened, does not show the functions in the right hand pane, nor does the +/- fold icons appear. As noted, so far it seems to be isolated to one script file. Others that I have opened have not exhibited this behavior.

On opening the file in the editor it looks like this:

If I select everything (Ctrl+A) and comment out the entire file, I get the list of functions to appear:

Uncommenting all the logic leaves the right hand pane populated, but the fold icons still do not appear:

I have deleted and completely recreated the file, but the behavior does not change for this file.
Any ideas about what might be causing this behavior?
Is this a known issue with this version?


See Coming in 8.1.18: Script editor improvements - #36 by PGriffith