If a video has another language track before the English track (i.e. French), then MCEBuddy will process the file, but keep the French track only. I have English (eng) selected in the system settings. But it seems to ignore that and always uses track 1 (even if properly labelled).
Possibly related, I read a post that said that if the video did not have the audio track labelled, that MCEBuddy would label it according to your language selection. This is not working for me, either. If the track is “unknown” (even though it is actually English), the resulting file stays “unknown”.
The file for which the logfile is attached below had French first, and English second. The resulting file was in French (labelled French, too).