Podobno rzeczywiście pomaga wyłączenie tej optymalizacji:
Following are the tips that have helped out number of people to fix sync issues with Google apps in Nexus phones:
Try disabling power savings mode for the apps that are giving you problems.Turn off Optimization for Gmail.Go to the Gmail app on your phone and go to the settings. Click on your email. Click on the “Sync Gmail” button So that itUNCHECKS. Then CLICK IT AGAIN so it CHECKS.