Somewhere along the line you had a previous file open that did have sleigh bells - of which that patch didn't get overridden when Sibelius loaded the patches for the current file - and Sibelius is incorrectly using that slot/channel. Doing a Playback Configuration "reset" should take of it.
Option 1: Create a new (or switch to a different) configuration.
Option 2: Trash the "Playback Configurations" folder inside the Sibelius User's directory, then restart Sibelius. From there you'll need to recreate your configs. (Sibelius will recreate the defaults for you.)
I've seen on a few occasions where Sibelius will somehow end up with a (or multiple) corrupted playback configuration(s). Instead of trying to troubleshoot which one (or more) is bad, it's probably easier to just delete the config folder (option 2) and start over. It won't hurt anything to do so, other than a little time to set things back up again.
Let me know how it goes.
Option 1: Create a new (or switch to a different) configuration.
Option 2: Trash the "Playback Configurations" folder inside the Sibelius User's directory, then restart Sibelius. From there you'll need to recreate your configs. (Sibelius will recreate the defaults for you.)
I've seen on a few occasions where Sibelius will somehow end up with a (or multiple) corrupted playback configuration(s). Instead of trying to troubleshoot which one (or more) is bad, it's probably easier to just delete the config folder (option 2) and start over. It won't hurt anything to do so, other than a little time to set things back up again.
Let me know how it goes.