Android 8.0 Oreo based OxygenOS update causes a new error on OnePlus 5 and 5T. Some users are reporting that that they are getting ‘Instantiate Action Error: Java Class not found’ error after updating their OnePlus 5/5T to Oreo. This error usually come up during an outgoing call and when connecting or disconnecting Bluetooth audio.
If you are experiencing the ‘Instantiate Action Error: Java Class not found’ error on your OnePlus 5 or OnePlus 5T when making a phone call or connecting to a Bluetooth audio, here is how to fix it quickly. It seems that the issue isn’t directly related Android Oreo update, it is an audio conflict between OnePlus Phone app and third party apps.
Several reports confirmed that the SoundAbout app was the reason for this error and the issue can be fixed by uninstalling this app.
However, if you are still facing the ‘Instantiate Action Error: Java Class not found’ error, even after uninstalling this app, you can check the issue by booting your OnePlus 5/5T into Safe Mode.
To boot your OnePlus 5/5T into Safe Mode, follow the below steps:
1. Press and hold the Power button until you see Power menu
2. In the menu, tap and keep tapping on the ‘Power off’ option
3. You will then be asked if you want to go to Android Safe mode
5. Simply tap on the Ok button
After rebooting your phone into Safe Mode, check for the ‘Instantiate Action Error: Java Class not found’ error by making a call. Most likely, you will not get the error. Now, boot your OnePlus 5/5T into normal mode and try uninstalling third-party apps to fix the issue. (Source)