Have you tried going into Song Settings and activating "Force Simple Arrangement" to see if that makes a difference? This may well stop some of the embellishment you're hearing.
That does nothing. This issue is still there and is very old.
The question is : basically, when we want a Cmaj7 chord, we write a Cmaj7 and we should get Cmaj7 ; when we want a Cmaj9, we write Cmaj9 and we should get Cmaj9. Ok, for the embellishements, but only at the request of the user and not by default.