I just upgraded from build 3180 to 3183 and suddenly my UI was huge.
I used to set "dpi_scale" to 1.6, but I notice that that doesn't seem to do anything anymore. Even removing that value doesn't make the UI smaller.
In order to fix it I had to add the "ui_scale" setting, and set it to a value of 0.7. Only then was my UI the correct size again.
So should anyone else have the same issue: don't change the dpi_scale, change the ui_scale.