Having the following issue:

In a score in Sib 8.6 I have some instruments to be played by Aria Player (Multi).

I see in my Sib. score, the mixer, that Sibelius assigns channels to the instrument tracks, also for those which are in the Aria player.

I start loading the instrument in Aria Player; when Sib tells me Bassoon is in the score to Aria Player channel 1, I load it there, the first trumpet is being assigned to channel 2 - I load it there. The 2nd. trumpet is being assigned to channel 13 (why -? Why not to channel 3 in the Aria Player?): I load it there, until everything is being assigned and 4 Aria channels are left.

I start playing the score and find I do not hear all the Aria-Instruments. I check again, and find that within the Aria player the channels have changed a bit

Suddenly the second trumpet sounds like a bassoon: The 2nd channel seemns to have loaded the bassoon sound without my interfering.

Any idea why is this so, and how can I stop that "spontaneous configuration", please?

Thanks.