I'm having a very strange problem with my phone, a refurbished Samsung galaxy a10e with Android 9.

About 5 - 10% of the time I don't get notifications for text messages. I go to send one and find two replies I've been waiting for, but there was no notification. I think I also miss some notifications from other apps, but I'm not sure because there aren't many that I expect. I installed a notification history app and it confirms that some notifications never appeared.

It happens in my preferred text app, and in the stock app. It happens when I'm not using the phone, and when I'm using other apps. I've searched the internet and haven't found anything about this problem. I've adjusted some settings like battery saver, but that hasn't helped. This phone is supposed to be able to update to Android 10, but it doesn't. If I could make it update, maybe that would help?

This is a new-to-me phone, so I could send it back. But I really don't want to start over with another phone. Can anybody suggest a way to fix this?