Welcome to AC!
Which LG phone do you have? Oreo is working fine on my Pixel 2 XL so it may be an issue directly related to the LG implementation on your device. I suggest taking a browse of the forum section for your device (we can even have your post moved there once you tell us which device it is so you can get directed help) to see if others are having the same issue.
Have you done a factory reset? While it's not a blanket solution to every problem, some devices just don't take platform updates as well as others and a factory reset (which is a misnomer as the phone will NOT go back to the Android version it had from the factory but will simply have the user data partition wiped) could well resolve the issue. Also - you can try clearing the cache partition from Recovery, but how you get there is also dependent upon which specific device you have.