If you're relying on the pinning of terms into other term sets you should know that it doesn't always work as expected.
The idea with pinning is that you maintain the term's children in one term set but surface it and its children in a read-only fashion in other term sets. It's an elegant way to present multiple arrangements of the same terms whilst maintaining single identity.
Usually it works
new term is
created beneath the source term, it is immediately propagated to all pinned instances as expected.
Sometimes it doesn't work
existing term is
moved from another termset to beneath the source term the propagation fails to happen. You may think all is well when you look at the "master" instance, but check the pinned instances and you'll find the new term does not appear there.
|Initial State||After Move of Pluto|
Both SharePoint 2013 on-premise and Office 365 are equally afflicted.
The only way to deal with this state seems to be to delete all the pinned instances and re-pin them.
We've logged this with Microsoft and will update this post if we hear about plans for a fix.