Some users of Nexus devices that are running Android 6.0 Marshmallow and up, which include the new Nexus 6P and Nexus 5X and the older Nexus 6 and Nexus 5, have reported syncing issues related to Gmail and Inbox.
The problem being reported is that notifications from Gmail and Inbox are not showing up properly, along with those from a few other apps. The notifications come in at a later time, and sometimes do not come in at all.
The issue has been added to the Android Open Source Project Issue Tracker, and at the time of writing, the thread has already been starred by 677 users. Representatives of Google have commented on the thread, which means that the Android team is working on a fix for the problem.
"I am intermittently not getting either Gmail or Inbox notifications for up to 12 hours at a time unless I open the app and manually force it to sync by pulling down," wrote a user who has a Nexus 5X and is on Google's Project Fi.
"Gmail notifications are delayed. I get the email's instantly, just no notifications for 5-10mins or more," wrote another user, who is using a Nexus 6P on Android 6.0.1 Marshmallow.
Another user on a brand new Nexus 5X that has been updated to Android 6.0.1 Marshmallow straight out of the box reported syncing errors with Google contacts, with only some contacts being properly carried over.
Many more users echoed the issue, mostly stating that the problem was first experienced upon the update to Android 6.0.1 Marshmallow.
Users have tried several workarounds to try to fix the problem, such as resetting the Google accounts registered in their Nexus devices, clearing the cache of the devices and undergoing a factory reset. These attempts were unsuccessful in having the notifications come in when they should.
A handful of users posted in the AOSP issue tracker thread that the problem could be connected to the Doze feature that was introduced to Android 6.0 Marshmallow. The feature automatically places the device in a sleep state when it is at rest and unplugged, with the screen of the device turned off. The system of the device tries to save battery by restricting the access of apps to the user's network and other services that are CPU-intensive. The system periodically exits Doze for short periods of time to allow apps to complete deferred activities such as syncs, alarms and jobs, allowing the apps to access the network.
Turning off the Doze feature was reported to be effective for some users, who claimed that by doing so, the notifications started to appear again on their Nexus device. However, the workaround is not applicable to all users, as there were some who tried turning off the Doze feature on their Nexus devices but still reported the same issues.
The problem is at the very least an annoyance for users, and could be considered a major bug for those who rely on notifications to inform them of important e-mails coming in. Users are advised to try turning off the Doze feature of their Nexus devices as a temporary workaround, and if that does not work, they could also look to download another app for managing emails.
The next security update for Android is coming up, and could be launched in the next few days. Hopefully, the Android team will include a fix to the problem in this update, or perhaps with Android 6.0.2 Marshmallow.