In case you ever stumble over error messages like
CodeSign /Users/.../Library/Developer/Xcode/DerivedData/mobileapp-dqzeepmlgrwdlnamvfpcsigcnoil/Build/Intermediates.noindex/ArchiveIntermediates/mobileapp/InstallationBuildProductsLocation/Applications/mobileapp.app/Frameworks/TNSWidgets.framework (in target 'mobileapp' from project 'mobileapp')
CodeSign /Users/.../Library/Developer/Xcode/DerivedData/mobileapp-dqzeepmlgrwdlnamvfpcsigcnoil/Build/Intermediates.noindex/ArchiveIntermediates/mobileapp/InstallationBuildProductsLocation/Applications/mobileapp.app/Frameworks/TKLiveSync.framework (in target 'mobileapp' from project 'mobileapp')
CodeSign /Users/.../Library/Developer/Xcode/DerivedData/mobileapp-dqzeepmlgrwdlnamvfpcsigcnoil/Build/Intermediates.noindex/ArchiveIntermediates/mobileapp/InstallationBuildProductsLocation/Applications/mobileapp.app/Frameworks/TNSSideDrawer.framework (in target 'mobileapp' from project 'mobileapp')</p>
when building an iOS app with fastlane (in this case, implemented with NativeScript), try to manually unlock the keychain in your build:
security unlock-keychain -p $CERT_KEYCHAIN_PASSWORD
In my case, that helped in the end – manually installing WWDR certificates and other hints I found did not.