Going through the official announcement thread at the OnePlus community forums, I noticed that some users are claiming that the update still has a few issues including a screen flickering problem, auto brightness not working correctly, and a couple of users even reported that they had poor performance in games compared to the previous build.

The update is not available for carrier variants of the OnePlus 6 such as the one sold by T-Mobile. Users upgrading from an older build or beta version may have to delete the user data before installing the new firmware, so you should back up your files to prevent loss of important data. If you are still on OxygenOS 10.3.12, you will need to download the full package for OxygenOS 11, which weighs about 2GB. Or if you are impatient and want the update immediately, you can use the Oxygen Updater app to download the incremental patch which is reportedly only about 180MB in size, and install it manually. If you haven't received the OTA notification, try to check for the update manually.

The OxygenOS 11.1.1.1 update for the OnePlus 6 and OnePlus 6T is being rolled out in batches, and could take a while to reach all users. Annoyingly, it does not go into the details about which issues were fixed. The change log posted by OnePlus, claims that the new build includes some improvements toward the stability of the system, and that it has fixed some known issues. OnePlus says that the stability of the network connection has been optimized, it's not clear if this relates to the mesh network issue that users had been complaining about. Both of those fixes should, on paper, offer a better gaming experience. The release notes for the firmware states that the power consumption of the devices has been optimized to reduce heating, and that the gyro sensor's sensitivity has been improved. The update arrives with the September Security Patch for both phones. What's new in the OxygenOS 11.1.1.1 update

For those unaware, OnePlus released the stable version of OxygenOS 11 for the OnePlus 6 series in August, after testing the beta version for about 5 months. OnePlus is rolling out the OxygenOS 11.1.1.1 update for the OnePlus 6 and OnePlus 6T.

Oneplus 6 oxygen 9.04