A little confused with your terminology of System Preferences. I’m assuming you mean Settings (on iOS 14).
There was a similar problem reported over a year ago, back on either iOS 12 or 13. Seem to recall Leo mentioning being annoyed by something similar during that timeframe. Seems like it went away with an update.
So first question is what version of iOS are you running? You might be able to update to a newer version. Check under Settings/General/Software Update.
Other suggestions beyond what you have already done can be painful. Before doing any of them, highly recommend you backup the iPhone to a Mac or PC using iTunes (pre-Catalina on Mac) or Finder if on a newer MacOS. Be sure to select the encrypted backup selection, as this will preserve passwords and settings for when you recover the backup. Also, in case you get to my last option below, I suggest you do a screen shot of each page of your iPhone screen, including opening and recording any folders. Move these photos to another device in case you need to manually recover the iPhone. Also, don’t procede with any of these until you know you have access to all requried passwords and user names.
First option would be to perform a Backup Restore. A bit painful, as apps have to update online after the restore. Also, if you use Apple Pay, you need to go into Wallet, and go through the authorization process for each credit card.
If that doesn’t fix it, the full Restore process is the final option. Requires putting the iPhone in Restore mode, which is not obvious if you just press the Restore button on iTunes or Finder. Best to google “iPhone Restore mode” to get procedure for your specific model. After doing the Restore, during the iPhone setup, you select the option to restore from a backup.
If this doesn’t fix it, there is one more option. Do the Restore again, but do not select the backup restore option. This one really hurts. You have to manually setup and install everything. And this is when you need the screen photos I mentioned before. Also, if you use an Authenticator like Google, and you did not save the QR code or multi-digit code for each, you may have to log into every account that uses it and create new codes.
I have literally done the last three procedures multiple times in the last 2 weeks trying to recover from a disastorous beta update.