Having worked some more on the layout, I have come up with
a potential alternative solution to the issue encountered, and also have a hypothesis on the source of the issue.
I believe that the problem emanates from any frame
that isn't securely attached to one of the physical edges of the screen. Anything attached to those, however indirectly, reacts accordingly when screen resolution changes take place. Only those 'floating' on the screen do not realign correctly when the resolution is changed.
The alternative I have come up with is simple, and yet something of a handful for the author. Basically, switching between resolutions and realigning these two frames manually,
creating a new exported UI for each resolution (or for a selection of resolutions most commonly used). The drawback to this is obvious : the author will suddenly go from having one layout to two, three, or more. All of which will need editing.
It's either that or a. telling the users that if they want it to work they have to realign it themselves, b. finding a way to configure the layout so as to attach the two frames to frames connected with the edge of the screen (impossible in my case).