The REST API (the backend for the mobile apps) delivers highly outdated content on some pages. While this seems to be rare, one page affected is Wikipedia:Administrators' noticeboard/Incidents. As of May 2022, mobile app users see versions lagging ~5 days behind, so they won't be able to reply in any threads there in a timely fashion.[15] Formerly, this issue was worse, displaying content from September 2020 in 11 April 2021.
When using the Minerva skin on the desktop domain (example), notifications that are not alerts are not shown when opening the notification area. (T306737) This means notifications like "thanks", "(pagename) has been reviewed" and "(user) replied in (topic)" are not shown. Mentions and talk page message notifications are alerts, so those are not affected.
Notes
^ abUsers with a confirmed email address will get an email by default. This can be turned off in their preferences.
^Shown in Vector (default), Monobook, and Modern skins. Looks like other alerts in Timeless and MinerveNeue skins.
^Alert should appear on non-mainspace pages, and any time the user taps "edit". However a caching bug often prevents the alert from showing.