As per #9560 where previous issues regarding this were collapsed into.

If you have one monitor with non-100% scaling and one monitor with 100% scaling both setSize and setPosition do not act as expected (they always set incorrectly by a factor exactly equal to the scale factor of the screen)

A proposed workaround is #9708 but that simply reverts the addition of the feature instead of fixing the underlying cause.

All future issues regarding DPI scaling and window positioning / sizing should be merged into this one.