Subtitle opaque box background drawing issue

[bibsp]

Issue:

Reason:

Subtitle file:

Drishyam (2015) (1080p BluRay x265 Natty).zip

[adipose]

Libass or no?

[bibsp]

Without libass

[clsid2]

Happens with outline set to 50% transparency.

[bibsp]

It happens always. Visible when it is transparent.

I found if full sentence is italic, it works fine.
If a part of sentence is italic then this glitch happens.

<i>test test test test</i> this will work fine.

test <i>test</i> test this will have issue.

I created a test subtitle.

test.zip