Same behaviour with the beta toggle.

I'll look into that, user preferences update happens as a deferred update (it's executed as a last thing during page request). Same happens with the Beta switch. I think that can happen when prod is bit overloaded, and server renders you a new page, but the properties update didn't finish yet. Thats why it renders as "off" state (because switching to ON is still in progress).

I'll update the code to update the database before it returns any content to the user.

Change 498943 had a related patch set uploaded (by Pmiazga; owner: Pmiazga):
[mediawiki/extensions/MobileFrontend@master] Update user preferences before flusing output.

https://gerrit.wikimedia.org/r/498943

Change 498943 merged by jenkins-bot:
[mediawiki/extensions/MobileFrontend@master] Update user preferences before flusing output.

https://gerrit.wikimedia.org/r/498943

@Jdlrobson Where do I test this? I am still seeing this behavior in Prod.

Beta cluster
https://en.m.wikipedia.beta.wmflabs.org/w/index.php?title=Special:MobileOptions&returnto=Special%3AContributions%2FUnban+Reguyla

Test Result

Status: ✅ PASS
OS: iOS
Browser: Chrome on (iPhone XS Max)

Test Artifact(s):