Since almost four weeks now last version isn't 2.20 but
version 2.21.
Some changes were made in 2.21 with respect to subtitles.
So perhaps download latest version.
Further a question: did you happen to see these threads?
http://bsplayer.com/forum/viewtopic.php?p=37321#37321 http://bsplayer.com/forum/viewtopic.php?p=37748#37748
PS: When diacritic characters are no longer shown, could you please check which font "script" is used?