resizeViewPortTo resizes to the wrong size most of the time in Safari 14

[Artur-]

Running

    @Test
    public void sizeTest() throws IOException {
        testBench().resizeViewPortTo(1550, 850);
        testBench().compareScreen("hello");
    }

on Saucelabs with various browser versions produces

error-screenshots/hello_mac_Safari_13.png:      PNG image data, 1550 x 850, 8-bit/color RGBA, non-interlaced
error-screenshots/hello_mac_Safari_14.png:      PNG image data, 1535 x 850, 8-bit/color RGBA, non-interlaced
error-screenshots/hello_windows_chrome_87.png:  PNG image data, 1550 x 850, 8-bit/color RGBA, non-interlaced
error-screenshots/hello_windows_firefox_84.png: PNG image data, 1550 x 850, 8-bit/color RGBA, non-interlaced
error-screenshots/hello_windows_msedge_87.png:  PNG image data, 1550 x 850, 8-bit/color RGBA, non-interlaced

for some reason, Safari 14 is 15px narrower than all the others. This happens most of the time, in some cases Safari 14 is the correct size.