Unfortunately, you have been selected to participate in another one of Roku's unasked for "test features".
From what I have previously read, allowing Roku to automatically decide channel/app tile placement is to assure that your most used channels/apps will always be at or near the top of the screen.
I think most people prefer to arrange their tiles according to the own preference.
Since most of these test features are a "work in progress", it will probably just keep overriding your preference when set to manual and you will likely just have to deal with it until their testing phase is over (or at least addressed by Roku during the course of this testing).
I do feel sorry for you. Roku should not be using their customers as beta testers without their acknowledgement/consent.
I remember there was a setting somewhere, possibly in one of the "secret" menus, that you could prevent your device from being in beta testing features. Can't find it right now.
I just have a feeling that if this feature was for the convenience of the user, then Roku would provide the options for "alphabetical", "most used", "most recent", etc.
I suspect some "preferred partner" channels will find their way onto the Home Screen or pushed towards the top.
With the continuing shift of Roku into an advertising platform, the Home Screen has become their own little playground at the expense of user experience at times.
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There was a "cycle software update server" menu item that used to have the options for beta and release but the ability to toggle/cycle between them was removed/disabled a number of updates ago. I am not sure, but I think you had to be in the official beta program for the beta option to proceed successfully. (that menu item was under the 3FF, 2Rew procedure if that was the one you were referencing.)
