Hi Alejandro,
the issue had disappeared for most merchants, but recently (last 1-2 weeks) we’ve gotten support requests again with the same issue. It’s only affecting some stores, i don’t think it’s theme related.
My best guess would be that there is some deeper technical issue in the shopify backend with the line item properties being dropped on the checkout flow. (maybe firewall or some load balancing component).
Either way this issue is very annoying for merchants and for partners handling support requests.