As mentioned above, you have to tell the 561 what it's default surround mode is; even if you change the mode, selecting that source will default back to that mode.

You can do this in the config programme.

You can have two (or more) defaults for the same input by setting up phantom inputs; use a separate source button and set it to the same physical input; again, this can be set in the config programme.

If you have a flaky source and the 561 loses sync on the digital stream, it can go back to the default surround mode when sync is restored; this happens on my 568.

All the best,

Steve