I managed the settings but the same issue left. The problem stays for any notification but only on the lockscreen. When I am the only one with this bug, I think I have to do another clean flash with formatting the phone.
I'm having the same problem. It will only display the notification count message (for all apps) while the device is locked. If I unlock it (e.g. using face unlock) while staying on the lock screen the real content is shown. For example I activate the screen -> "1 new notification" -> I move my face in front of the camera -> "Text.. text.. text..". It appears to be some kind of security/privacy feature, but I haven't found a place to turn it off either.
Thanks for your help. Messages at the lockscreen are set to "show full content".
I tried some settings as mentioned before and when I stay at the lockscreen after recognizing my face, the content is shown. So that is working. But when I put my phone to "do not stay at lockscreen after recognition" no content is shown. Perhaps that is a wanted security setting.