Cannot connect to shadowcljs repl

Steps to reproduce:

1. lein new luminus luminus-app +re-frame +shadow-cljs +aleph
2. lein shadow watch app
3. shadow-cljs cljs-repl app

In step 3, we get the error:
2019-07-17 13:53:11,006 [main] INFO org.xnio - XNIO version 3.7.0.Final
2019-07-17 13:53:11,103 [main] INFO org.jboss.threads - JBoss Threads version 2.3.2.Final
2019-07-17 13:53:11,122 [main] DEBUG io.undertow - Configuring listener with protocol HTTP for interface 0.0.0.0 and port 9630
[2019-07-17 13:53:11.170 - WARNING] TCP Port 9630 in use.
2019-07-17 13:53:11,178 [main] DEBUG io.undertow - starting undertow server io.undertow.Undertow@f1b70d5
2019-07-17 13:53:11,198 [main] DEBUG io.undertow - Configuring listener with protocol HTTP for interface 0.0.0.0 and port 9631
[2019-07-17 13:53:11.722 - WARNING] :shadow.cljs.devtools.server/nrepl-ex
BindException Address already in use (Bind failed)
java.net.PlainSocketImpl.socketBind (PlainSocketImpl.java:-2)
java.net.AbstractPlainSocketImpl.bind (AbstractPlainSocketImpl.java:387)
java.net.ServerSocket.bind (ServerSocket.java:375)
java.net.ServerSocket.bind (ServerSocket.java:329)
nrepl.server/start-server (server.clj:128)
nrepl.server/start-server (server.clj:96)
shadow.cljs.devtools.server.nrepl04/start (nrepl04.clj:376)
shadow.cljs.devtools.server.nrepl04/start (nrepl04.clj:359)
clojure.lang.Var.invoke (Var.java:384)
shadow.cljs.devtools.server/start-system/fn--31019 (server.clj:331)
shadow.cljs.devtools.server/start-system (server.clj:301)
shadow.cljs.devtools.server/start-system (server.clj:242)
shadow-cljs - server version: 2.8.39 running at http://localhost:9631

Reproduce the failure with the three commands in the issue and inspect the shadow.cljs.devtools.server.nrepl04/start path named in the stack trace. Determine how the existing listener on ports 9630 or 9631 is handled, then verify that starting the REPL no longer fails with an address-in-use error.