I could give you one more suggestion to try, i.e.
either try a different overlay setting in the "Options"-"Preferences"-"Video" menu if you have perhaps selected the option "Draw subtitles to overlay surface" on the "Subtitles" tab of "Preferences"
or if "Use overlay" is not selected at the "Video"-tab, make sure that "Draw subtitles to overlay" at "Subtitles"-tab is also deselected)
Maybe that does the trick!
(Ik hoop het)