When automatic commercial skipping is enabled (set to always in preferences) and file/recording is not seekable -> playback is not possible.
Player loads the skiplist (from commercial flagging) than tries to seek (as instructed by always skip setting) and immediately fails as seeking is not possible. Program than complains via message box. There is no way how to prevent this as it happens automatically after recording selection.
Solution -> Automatic commercial skipping should be disabled for non seekable files/recordings.