In #48698 we added a new endpoint navigation-fallbacks (plural). We should rename to navigation-fallback singular as it's not a collection.

Sorry, if it's not too much trouble can we change the REST API route from navigation-fallbacks to navigation-fallback in a follow-up PR? I keep reading the endpoint as returning a collection, when it's in fact an item endpoint.

Originally posted by @TimothyBJacobs in #48698 (comment)