I had a horrible problem. After weeks of trouble shooting and searching the web for an explanation.
So I ended up setting it up as a new phone. Then sign into iCloud. Then redownloading all my apps! I had to basically clear everything out! Every time I get a new iPhone I do a did a set up using my iCloud back ups. You have to make sure your contacts, music, photos, notes, calendars..etc are all backed up in iCloud. So after seven years of new iPhones every year I somehow got a corrupt file and apps . I figured out that when I went to download my apps some were not able to be downloaded because the app makers didn’t keep them updated for the next iOS..etc. Abd since I was restoring from my backup I kept getting the apps that were not updated. It works perfectly fine, in fact great! Just like an iPhone should. I talked with Apple care and they told me that this happens many times to people. They said what I did is exactly correct in fixing it. Good luck! 👍-1F3FB;