Multiple reports are suggesting that iOS 12 may have a bug, causing periodic and random issues with devices not charging when plugged in to a power source, or placed on a wireless charging pad without user interaction.
AppleInsider – Frontpage News
Apple Day – Apple, iPod, iPad, iPhone, iTouch, iMac, iBook
Apple Day – Apple, iPod, iPad, iPhone, iTouch, iMac, iBook