I found what the problem was and how to fix it. You need to disable the mono settings in the options of the android part of your project to fix it. After this you need to remove the app from your phone and you can debug your app again.
It is a known bug with the oneplus phones.
The answer and bug report can be found if you google:
Attempt to re-install Mono.Android.DebugRuntime without first uninstalling.