Embedded subtitles in mkv can't be disabled

[Belsen]

BS Pro 953

Manually embedded SRT subtitles into MKV file.

While playing, subtitles can't be disabled, neither with "S" key nor with Subtitles -> Show Subtitles (bsplayer main window shows "No subtitles" though).
No subtitle filter installed, no VobSub, you still can change font/color/position/delay of subtitles in bsplayer - you just can't turn them off.

Known workarounds:
1) Disable subtitles at all
Options -> Preferences -> Subtitles -> Subtitles disabled (requires player restart).
2) Load an empty external subtitle file (like nosubtitles.txt created with notepad with just a caret return in it).
3) Shift them after the end of movie
Subtitles -> Subtitle properties -> Manual correction -> 10000 secs.