Preference dialog visual glitch

Check the left hand panel, when moused over the items will appear. Cannot reproduce, has been happening irregularly for a few weeks now.

Does it happen with the default colors/theme? Looks like it's configured to draw black on black or something.

Not sure.
Here is the theme I am currently editing.
Alt Dark.dlt (15.5 MB)

There is no simplified dialog colour settings and remembering all the different names for all the different parts of a dialog is difficult, as usually it's 'set and forget'.

Please check if I have changed any dialog settings and post the relevant settings so that I can fix them.

Theme/colors seem fine here, so it's probably something else. Not sure what would cause that though.