Subtitles: External vs. Embedded

Hello everyone.
Serviio ver. 1.4.1,
TV Samsung UE65HU8500RU (native support for .ass subtitles)
Trouble with subtitles: .mkv has embedded english subtitles and also has an external russian subtitles in .ass format, but shown only embedded english.
Preferred langusage in Serviio Console is set to ru,rus,russian.
In Serviio support page mentioned: In the case a video has both, a matching external subtitle file as well as a matching embedded track, the external file has priority. But it doesn't.
How to fix? Thank you.
* sorry for my english
Serviio ver. 1.4.1,
TV Samsung UE65HU8500RU (native support for .ass subtitles)
Trouble with subtitles: .mkv has embedded english subtitles and also has an external russian subtitles in .ass format, but shown only embedded english.
Preferred langusage in Serviio Console is set to ru,rus,russian.
In Serviio support page mentioned: In the case a video has both, a matching external subtitle file as well as a matching embedded track, the external file has priority. But it doesn't.
How to fix? Thank you.
* sorry for my english