More than likely the download became corrupted during installation I recommend you do a clean install of iOS 11.0.3 and then set up your device as new and not from a backup. Yes, it’s an inconvenience, but it will more than likely solve the problems “you” have been experiencing.
This. Best advice in this thread.
If system files become corrupt when overwrites occur (installing updates over the top of current system files), then you're going to experience all types of different issues. The only way to remove those corrupt system files is to completely wipe the phone and install a fresh copy of the operating system. Nine times out of ten this resolves the majority of issues.
Problem is fresh install does not solves bugs in an OS.
There's a difference between bugs and corrupt files wreaking havoc. Corrupt system files can be fixed by the end user by installing a fresh copy of the OS. Bugs can only be fixed by Apple developers.
Yes, there are still a small handful of bugs with the current version of iOS, but no where near what they were when the beta was first released. The only way to narrow it down and find out whether or not it's a bug is to set the device up with a fresh install of the OS.