OnePlus has begun the rollout of OxygenOS 5.1.2 for the OnePlus 5 and 5T today, bringing a number of fixes and improvements to the devices. The update is just over 1.6GB in size so it will be one that you will need to download via WiFi. Also keep in mind that the update was released over the weekend and it is being phased out to users as OnePlus normally does. If you don’t see the update on your 5 or 5T yet, it is just a matter of when it gets to your device.
The OxygenOS 5.1.2 update, from a feature perspective, brings a couple of new features according to the release notes. First, in the Gallery app, you will now find a “Recently Deleted” collection of photos you have deleted from your phone. This makes it easier to find them should you want to recover them (I still recommend using Google Photos).