Android Core Apps/Contact Storage draining battery? Try this.

[B. Diddy]

My wife's Pixel XL was draining battery, and I saw that "Android Core Apps" was using an inordinate amount of battery. When I tapped it, it showed that it was Contact Storage causing the problem. It may have been due to WhatsApp and WeChat trying to sync contacts (although I'm not sure what might have been causing the process to work overtime). I turned off Contact Sync for both of those accounts (in Settings>Accounts), and the battery drain seems to have resolved.