FCM Push Notifications not being received on some Android devices

We are using the latest version of the Push plugin for notifications and when we test the application on a range of test devices (Android 5, 6, 7 and 8) they work all the time. Many of our users though (particularly Android 7 and Android 8 users) are reporting that they are not receiving notifications. Does anyone have a similar experience? I am in the process of trying to contact a user so we can monitor token creation and notification send logs on the server but wondered if anyone has had similar issues with the plugin?

We have the same kind of issues for Android 7 and 8. Did you get any clue?