İ character Subtitle on video preview

[senna23]

if there are two lines on subtitle entry, on first of which there is an İ character, the subtitle is shown on video preview as on the the first photo.
if i delete that İ character, square vanishes, but space between two line is bigger than any other two lines.
if the second line has it, there is no problem on preview as on third photo.

PS: subtitle in Turkish, encoded as UTF-8.