https://eclecticlight.co/2019/07/25...-for-sierra-and-high-sierra-security-updates/ Security Update 2019-004 for Sierra and High Sierra may cause problems with sleep. Either activating or waking up. Already mentioned on Macintouch and above website; MacRumors, AppleInsider, MacObserver totally mum about this MAJOR issue. MacSurfer News points to above website. Edit: appears to be related to an update to the BridgeOS powering the T1 and T2 chips. Mostly 2016-2018 MacBooks and Mac Mini 2018s affected.