I’ve found the same issue. However, I don’t think it’s as simple as only 16:9 that works. I’ve been working at other resolutions but I’ve found specific resolutions cause the issue above (and other really odd behaviour). One resolution that causes it for me is 4620 * 1080 (4.28:1 aspect ratio) whereas 7680 x 1795 (also 4.28:1) seems ok.
It also seems that resolutions below 4096 allow any aspect ratios (at least for the variants I’ve tried) without distortion. Above this it becomes extremely unstable. Even 7679 x 1795 (1 pixel difference to the resolution that works) causes a huge offset. I’ve put in a bug report and quoted this page