I use rasplex for about two month now and everything worked fine. Yesterday I started a movie but my receiver was very quiet and the dts / Dolby sign didn´t show up (just PCM). Then I tried 5 other movies -> same result
I changed nothing. In Audio settings there is DTS and AC3 compatible Receiver enabled.
Today I saw a new (?) Message after I started the rasplex, it says: "Puls eight cec adapter found" .... and something with configured....
Since the message mentions the CEC adapter, it may be a good idea to go through its settings and disable any CEC interactions you don’t need. You find the adapter entry in the submenu: Preferences > System > ‘Input devices’ > Peripherals. Pressing ‘Enter’ with the CEC adapter selected will open a submenu dedicated to CEC control settings.
However, if those settings are involved, they should have had the same effect earlier. Since you say you’ve changed nothing, there is no reason for any RasPlex behavior to change. The CEC adapter should have been found in EVERY boot session, without exception (assuming you connect TV by HDMI).
Were any of the 6 movies you mention testing with this result also played in earlier sessions with different results ? If not, please test one of the movies you’ve earlier played without this problem, to see if its playback has changed. (This based on the idea that something about some movies may trigger the problem.)