Thanks for providing the domain name. We did give it a look.
The difference is that how domain names are configured on Afternic nameservers. So you point your domain name to ns1-ns2.afternic.com nameservers. But in the zone file of those nameservers, they put NS records with ns1-2.namefind.com values. Unlike Sedo, where they have same values both in recursive and authoritative nameservers.
Here is the dig result for your particular domain name:
So how does this work. We see that you pointed your domain name to ns1-ns2.afternic.com nameservers. And we start checking whether the world actually sees that your domain name is pointed there. But in responses that we get from the zone file, we assume that domain name "is pointed" to ns1-2.namefind.com nameservers. And thus propagation check fails and we receive a "non-propagated" domain name.
So this is the case where we developed our tool assuming of correct configuration of nameservers but it fails it here. We will think how to solve this particular use case so that it is clear on UI what's going on.
Really appreciate you bringing up this case, helps us to think more ways to improve our service.