regression: DTS audio no longer plays in DVD VOB files.

I can no longer play DTS audio from a DVD VOB file. I was able to play the audio before.
I play the audio through the Digital (S/PDIF) optical connection to my Sony receiver STR-DE975.
AC3 5.1 plays fine on these VOB files. I have the DTS capable receiver checked in the audio capable receiver setting on the BB. Strangely, I can get one of the VOB files to play DTS 5.1 if I start playing the file in AC3 5.1 (audio stream 1 English) and change it to audio stream 2 English).
Then rewind a bit as it plays the video plays fast and the go to the audio settings and it says Audio stream 2 is now Unknown - AC3 5.1. Now audio stream 1 says Unknown - DTS 5.1. I choose the new stream 1 and my receiver tells me the Audio is now playing DTS 5.1. T
his does not happen in any other VOD video file with a DTS stream.
I had an issue with DTS not working using BB firmware version 1.1.0.19336.
I do not recall the version that fixed the DTS issue but the problem has returned again.