rules aren't correctly unifying

The problem: walk references until finding the root reference.

This example returns {:id :a :root 1} in the results as expected for datomic, but fails in datascript:

(let [c (db/empty-db {:id {:db/unique :db.unique/identity}})]
    (db/q '[:find (pull ?root [*]) :in $ ?id % :where [?e :id ?id] (root ?id ?root)]
          (db/db-with c [{:id :a :root 1} {:id :b :parent [:id :a]} {:id :c :parent [:id :b]} {:id :d :root 2}])
          :b
          '[[(root ?e ?e) (not [?e :parent _])]
            [(root ?e ?r) [?e :parent ?p] (root ?p ?r)]]))
;; => ExceptionInfo Insufficient bindings: none of #{?root} is bound in (not [?root :parent _])  clojure.core/ex-info (core.clj:4739)

This example throws an ArrayIndexOutOfBoundsException in datomic 🤷‍♂️ while in datascript returns too many results (however did it reach {:id :d}?):

(let [c (db/empty-db {:id {:db/unique :db.unique/identity}})]
    (db/q '[:find (pull ?root [*]) :in $ ?id % :where [?e :id ?id] (root ?id ?root)]
          (db/db-with c [{:id :a :root 1} {:id :b :parent [:id :a]} {:id :c :parent [:id :b]} {:id :d :root 2}])
          :b
          '[[(root ?e ?e) [?e :root _]]
            [(root ?e ?r) [?e :parent ?p] (root ?p ?r)]]))
;; => ([{:db/id 4, :id :d, :root 2}] [{:db/id 1, :id :a, :root 1}])

The issue names no source files or tests. Reproduce both recursive-rule examples through db/q, then trace rule evaluation and unification from that entry point; done means the first query returns the expected root and the second no longer returns the unrelated entity or throws.