Perhaps you, guitarrap, have Second Faulty Device as Well?
Take this in for a Genus Bar Appointment: If you purchased this from Apple, locate your nearest local Apple Store and take this phone in for a “Genius Bar Appointment". It's either no more than a software configuration error. If not, it is a hardware issue. What ever the cause, they
ll look at it.
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Provide this as Feedback to Apple:
Go Here: Feedback - MacBook Pro - Apple
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If Need be, Reinstall the macOS:
Perhaps the update did not successfully install.
Go Here: How to create a bootable installer for macOS - Apple Support
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Scan your Mac for Malware: Malicious Software:
Malware is malicious software that makes your device act in a mislead-manor.
Download this: MalwareBytes for Mac. Then update MalwareBytes for Mac and run it. Remove what is found.