I think spotted an example of federation failing between lemmy.ml, even after the update to 19.2, and Lemmy.world, which is still on 18.5.
If you look at the TenForward community on lemmy.ml (https://lemmy.ml/c/tenforward@lemmy.world?dataType=Post&sort=New) and compare to its lemmy.world version (which is its home) (https://lemmy.world/c/tenforward) … you’ll see lemmy.ml is behind about 2 days.
Haven’t seen any other examples like this, even from lemmy.world though I haven’t gone looking for them either.
I’m not sure what the exact circumstances are here, but something to note is that upgrading to 0.19 will mostly just help with outgoing federation (0.19.2 is much more reliable and robust when delivering activities to other instances compared to 0.18). We will start seeing the full benefits of this as more of the network upgrades.