Windows DPI scaling and component positioning

We are placing some buttons on the screen with a one pixel spacing between them that is supposed to show the black parent component behind.

Here’s how it looks on the Mac (looking HOT I think !)

In the following scaled Windows examples I have set the background to yellow to make the issue clearer:

125% scaling:

And at 150% scaling:

Anyone any ideas why I’m not getting my one pixel gaps?

100% scaling on Windows, after a reboot: