I chatted with Subbu and he couldn't identify any Parsoid issues around this page/revision or related Parsoid errors in production.

Could this have been a temporary issue? We had a cassandra node fail earlier today, which might have been connected. I am currently unable to reproduce the issue.

Also, is there a specific reason why you are querying for a specific revision? Ever since we simplified the RB storage design, it's much more beneficial and faster to query for the latest revision rather than a specific one, so if there is no compelling case to use the revid, it'd be better not to supply it at all.

Weird; I still get the error after trying the request twice more just now.

There are a lot of tests like this in the mobileapps repo that request a specific page revision that's known to exhibit the specific issue under test, and I assume that's what's going on here. It's an antipattern; these should be reduced to local unit test cases. The mobileapps tests need an overhaul in general, but there's no time budgeted for that.

In this specific case, the criterion being targeted is "page contains a navbox." I don't think we need to go to a specific revision for that; it's hard to imagine the navbox suddenly disappearing from the enwiki Cat article. I think we're safe removing the specific historical revision from the request URL.

Change 535213 had a related patch set uploaded (by Mholloway; owner: Michael Holloway):
[mediawiki/services/mobileapps@master] Mobile-html: Remove specific revision ID from the navbox-stripping test

https://gerrit.wikimedia.org/r/535213

Related: T151091: MCS uses integration tests which are slow.

Also related: T231933: Make RESTBase tests not depend on production enwiki pages

Change 535213 merged by jenkins-bot:
[mediawiki/services/mobileapps@master] Mobile-html: Remove specific revision ID from the navbox-stripping test

https://gerrit.wikimedia.org/r/535213

When done with the fixing the tests if there is more actionable stuff to do move it back to the backlog @Mholloway