This issue happened on both current production and alpha.
=== Steps to reproduce
1. Go to [Internet_of_Things] article.
2. Click on "Other languages" and switch to "Traditional Chinese"
3. Click on "Other languages" again to switch to "Simplified Chinese"
Demo: https://youtu.be/EEUbsffazbw
=== Expected
Able to read [[ https://zh.wikipedia.org/zh-cn/%E7%89%A9%E8%81%94%E7%BD%91 | 物联网 ]] after switched to Simplified Chinese
=== Actual
An error occured
=== Stacktrace
2018-10-12 16:49:29.693 11679-11945/org.wikipedia.dev D/OkHttp: <-- 200 https://zh.wikipedia.org/w/api.php?format=json&formatversion=2&action=mobileview&prop=text|sections|languagecount|thumb|image|id|namespace|revision|description|lastmodified|normalizedtitle|displaytitle|protection|editable|pageprops&pageprops=wikibase_item§ions=0§ionprop=toclevel|line|anchor&noheadings=&page=IoT%E6%8A%80%E8%A1%93&thumbwidth=640&uselang=zh-hans (205ms, unknown-length body)
2018-10-12 16:49:29.695 11679-11679/org.wikipedia.dev E/org.wikipedia.page.PageFragmentLoadState$3: onFailure():358: PageLead error:
org.wikipedia.dataclient.mwapi.MwException: The page you specified doesn't exist.
at org.wikipedia.dataclient.mwapi.MwResponse.postProcess(MwResponse.java:28)
at org.wikipedia.json.PostProcessingTypeAdapter$1.read(PostProcessingTypeAdapter.java:28)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:39)
at retrofit2.converter.gson.GsonResponseBodyConverter.convert(GsonResponseBodyConverter.java:27)
at retrofit2.ServiceMethod.toResponse(ServiceMethod.java:122)
at retrofit2.OkHttpCall.parseResponse(OkHttpCall.java:217)
at retrofit2.OkHttpCall$1.onResponse(OkHttpCall.java:116)
at okhttp3.RealCall$AsyncCall.execute(RealCall.java:153)
at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
at java.lang.Thread.run(Thread.java:764)