And you're using BS.Player (Pro) version/build nr?
What type of subtitles are we talking about?
I assume in the past you never had such problem?
Any new video card drivers installed recently? (or auto-update?)
Are you using old or new subtitle engine or.. is
"Use new subtitle parser/renderer" selected/deselected under (rightclick >) Options > Preferences > Subtitles [Subtitle properties] ?
Also is "Enable drawing subtitles under image with EVR renderer" selected/deselected?
(What happens if you change that setting?)
What OS are you running on your PC?
What video "Rendering mode" do you use?
(rightclick >) Options > Preferences > Video > [Video rendering]