Whisper audio to text takes forever and is terrible quality

This feature used to work quite nicely for generating Slovenian subtitles, the whole process never took more than 30 minutes and the subtitles generated were not bad (using the "medium" model). Since the last update, it takes over 24 hours for a 45 min video and the subtitles are pretty much useless. Is there a way to fix this issue?

Thanks in advance.