Updated iTunes in 10.12.6 from 12.6.2 to 12.7 Booted from another volume, deleted 12.7, booted back and installed 12.6.2 All ok. Then updated to 10.13, then got error 45076
iTunes 12.6.2 is installed by default with 10.13, in a fresh installation of 10.13: iTunes 12.6.2 -> no error
sudo rm -rf /Library/Documentation/Applications/iTunes/Acknowledgements.rtf /Library/Documentation/iPod/Acknowledgements.rtf /Library/Frameworks/iTunesLibrary.framework/ /Applications/iTunes.app/ /System/Library/PrivateFrameworks/iTunesAccess.framework/ /System/Library/LaunchDaemons/com.apple.fpsd.plist /System/Library/PrivateFrameworks/CoreFP.framework/ /System/Library/PrivateFrameworks/CoreADI.framework/ /System/Library/LaunchDaemons/com.apple.adid.plist /System/Library/CoreServices/UAUPlugins/ADIUserAccountUpdater.bundle/ /System/Library/CoreServices/CoreTypes.bundle/Contents/Library/MobileDevices.bundle/ /System/Library/LaunchDaemons/com.apple.usbmuxd.plist /System/Library/PrivateFrameworks/AirTrafficHost.framework/ /System/Library/PrivateFrameworks/DeviceLink.framework/ /System/Library/PrivateFrameworks/MobileDevice.framework/ /System/Library/Extensions/AppleMobileDevice.kext/ /System/Library/Extensions/AppleUsbEthernetHost
sudo softwareupdate --ignore iTunesXPatch
https://apple.stackexchange.com/questions/299842/how-to-fix-itunes-error-45076