When UI scaling is set to anything higher than the minimum, some scriptui palettes behave very unexpected and are not useable anymore. More simple windows do work fine, though.
I suspect that some complex ui elements such as the ListBox trigger this behaviour, somehow confusing the layout manager. I found that a (palette) window is rendered too small if it includes a ListBox. Any attempt to resize the window by the user makes all elements go away (or the whole window in ID 2024).
In another case, programmatic positioning of the palette made it disappear. This works fine as long as UI is not scaled, so it is at least not a pure scripting mistake.
It would be a lot of work to rewrite all affected scripts again using UXP, so please fix this! Some more simple interfaces show that basically ScriptUI can work in the scaled mode!
The whole thing is not completely new, see https://www.indiscripts.com/post/2021/03/scriptui-vs-ui-scaling
I am using ID 2023 and 2024 on Macintosh.