Notifications on locked screen with "preview when unlocked" option on iPhone 13

I started to experience inconsistent behaviour of notifications from some messengers on locked screen. The device is iPhone 13 and I've recently upgraded to iOS 18.7.1, but I've spotted the issues on the previous (minor or patch) version.

The problem: notifications are just not showed, but only for specific apps. If I open the app, I see the unread messages.

Attempts to resolve this:

• restarting the iPhone (didn't help)
• updating the apps (didn't help)
• deleting and installing the apps (helps just after re-installation, but the notifications can start dissappearing again later)

! I haven't try the device settings full reset, though I've seen suggestions to do that for the similar problem. I don't want to mess up with passwords and resetting other staff hoping that this bug might be fixed in other way.

More details. I assume this problem has something to do with the specific notification setting: showing only preview on locked screen and expanding notification content when the device is unlocked (with face recognition in my case). This option of "expanding only when unlocked" was turned on by default on my device initially and I've enjoyed this. Recently, when the problem with notifications appeared and I was forced to reinstall some apps, I see that this default setting is gone. So when notifications start to appear on the locked screen again (after re-inslalling the app), they are fully previewed. But if I change the setting to "expand when unlocked" instead of "expand always", the notifications can disappear again. (Or cannot - this is not 100% consistent, but I indeed had several cases when there was a definite relation between settings change and notification break).

Just to add: notifications are not just something "useful and convenient"; sometimes they can be a matter of safety (for example, air raid alarms), so not having them displayed immediately is more than frustrating.

I would probably go on with device settings restart if I won't be able to find a better solution soon or get a helpful feedback from the Apple support team.