A little over a week after the initial Nougat-based OxygenOS 4.0 release, OnePlus has released a small update for the OnePlus 3 and OnePlus 3T. The new OxygenOS 4.0.1 build is rolling out to both devices currently and is primarily focused on addressing bugs and stability issues with the OS on these devices. As OnePlus does, the update will be released to a small number of users first then roll out to the larger population as confirmation all is well with the update comes into them.
As for what is addressed, probably the biggest news is the updated APN settings. After the initial OxygenOS 4.0 update, many 3 and 3T owners had network connectivity issues with their carrier. This update should resolve those issues. However, in the posting announcing the update, OnePlus is saying that if you still have issues, to manually adjust the APN settings or, worst case, report it to the product team at OnePlus with your phone model and carrier involved so they can help identify the issue and resolve it.
The Proximity Sensor during calls has also been fixed in this update. Now when you are on a call and hold the phone to your ear, the display will turn off. Finally, there are numerous fixes and other
stability improvements under-the-hood in this update. These issues are not specifically called out in the announcement but given the rush to meet their self imposed deadline of December 31st to get the original build out, it is not surprising to see a quick bug fix release with stability improvements so soon.
If you have a OnePlus 3 or OnePlus 3T the update will be coming to you via an OTA update. You can manually check for the update by going to Settings>About Phone>Software Updates. Again, it will only be rolling out to a small audience at first so it could be a few days before you actually see it available for your phone.