Pixelmator Pro 2.3 on Mac OS 10.15.7 Catalina. There is a bug that occurs when exporting an image again after it has been exported using a custom size. The image below shows (left to right) Finder thumbnails of the image exported at original size (2201 x 2201), exported with a custom size (2000x2000), exported again without changing settings (2000x2000), and exported with the setting put back to original size. As you can see, the first custom-sized export works correctly, but subsequent exports are cropped, even if the setting is "original size." The images are exported at the correct size in each case.
When I duplicated the image (within Pixelmator Pro), the first export once again had the original, non-cropped image.
Custom size export bug
2021-12-02 19:04:42