One consequence of OnePlus getting rid of the headphone jack in the OnePlus 6T is users lost the Audio Tuner option a.k.a. the equalizer. This only worked for wired headphones. So, unless you used USB-C headphones, you didn’t have access to the equalizer. Well, that’s being addressed today. Oxygen OS 9.0.7 brings the feature back for Bluetooth headphones. The update also improves Bluetooth and Wi-Fi stability as well as less power consumption on standby. Shooting in slow-motion should also be a better experience.
Some of the other bug fixes include display issues with the wallpaper on the lock screen. It’s an incremental rollout though so you may or may not see the update hit your device immediately.
Source: GSMArena