When using the feature "Auto select" in the main page and in the Settings page -> Experimental : "Auto-upload favorite page", let's say you pick Yuumi and then you trade champions with a Nasus, and let's assume you have one favorite page set in RuneBook for every champion in the game, instead of applying again the automatic upload for the favorite page of Nasus, it will keep the page of the first champion you pick, which in this example is Yuumi.
So ideally, the method that auto uploads the favorite page should also be called every time that you complete a trade with an ally
When using the feature "Auto select" in the main page and in the Settings page -> Experimental : "Auto-upload favorite page", let's say you pick Yuumi and then you trade champions with a Nasus, and let's assume you have one favorite page set in RuneBook for every champion in the game, instead of applying again the automatic upload for the favorite page of Nasus, it will keep the page of the first champion you pick, which in this example is Yuumi.
So ideally, the method that auto uploads the favorite page should also be called every time that you complete a trade with an ally