There is a bug in ChunkedCons. In Clojure ChunkedCons (correctly) always calls {{seq}} in chunked-next. In CLJS it's not done. But since ChunkedCons has to be lazy it pretty much always gets an (empty) lazy seq as the "more" part.
Bug:
`
(-> (map inc (vec (range 64)))
seq
chunk-next
seq
chunk-next)
`
Returns and empty sequence instead of nil. This hasn't surfaced yet since nothing calls chunk-next on a ChunkedCons (yet).