Not too long ago, OnePlus released the third Open Beta for the 8 and 8 Pro, bringing various bug fixes for the Ambient Display and Zen Mode and making Canvas compatible with the new always-on Ambient Display. Now a bug has surfaced that deletes user data from some people who have joined the beta program. It looks like some 8 and 8 Pro owners have received the stable build of Oxygen OS instead of the Open Beta 3, which leads to the data loss.
If you see the Oxygen OS 188.8.131.52 update pending instead of the Open Beta but haven't restarted your phone yet to install, there's a workaround: You can get a specially developed KeepData app that prevents you from losing your files, available on the OnePlus Forum and APK Mirror. Install it, run the application, and hit the "KEEP DATA" button. Even when you've gone through this procedure, OnePlus still recommends you back up essential data on another device or in the cloud before restarting to update. A full backup via OnePlus Switch is also highly encouraged.
If you're already running a beta build, double check that it's the Open Beta you're receiving via OTA and not the stable Oxygen OS 184.108.40.206 build. If you're willing to switch from stable to beta despite this fluke, you can follow the instructions here. The Open Beta 3 downloads are also available on the OnePlus website for the OnePlus 8 and the OnePlus 8 Pro.
- OnePlus Forums