I've been using light room (not classic) version for over a year & never had a problem with exporting until about 4 months now. Not sure if its the recent update but It seems like the images that I cropped have been disproportionate in exporting. While I'm in the program its fine.
No problem when viewing my Mac computer Or android cellphone app.
But when I share the link to the images only the ones I did some cropping to seam to come out stretched out disproportionately. Its really annoying & now whenever I send my clientele the link to the photos online some are stretched out. its a major problem!