Ascending order is wrong, descending is right

I have made a shared web gallery from one of my albums with old scanned photographs. I have manually entered an approximate capture date in LR Classic for all pictures, and they show up in correctly in ascending order in both LR Classic and synced to LR CC. But in the web album all photos just come in the order I have added them, not ascending by date taken. The weird thing is that if I push the button up in the right corner to change the sort direction, they show a correct descending order. Is this perhaps a kind of bug?