That's a pretty normal log entry. We don't (currently) attempt to fetch parents for comments. When you subscribe to a new group, you'll get a bunch of comments for posts you don't have, but as the group rolls over and new posts come in, everything should work.

I think you just need to wait a bit longer. If you're getting comments, even if we're not currently saving them, that's a good sign everything is working. The posts will get there eventually.

The slow start is not ideal, but I don't think it indicates anything wrong.