I tried to extract the subtitle from a m2ts file but I receive an error message even if tsmuxer can do it without any problem, in fact I did it manually.
I don't know if it's a bug.
I wanted to encode a second Blu-ray but when I click to create the job an error message pop up about invalid GUI state.
Those are rare, haven't seen one for ages.
From the looks of it, this happens when Hybrid tries to extract subtitle from "N:\BDMV\STREAM\00004.m2ts" and decides it can't.
Not sure why it's not using tsMuxeR or ffmpeg => will look at it after work and report back.
Looks a bit like you are using the Subtitle->Tab to load an .mpls file and then try to extract the subtitles through there, instead of using the controls on the Base-tab.
Cu Selur