Xcodebuild -showBuildSettings timed-out

This seems to be a fastlane bug, I’d suggest you to open an issue on their tracker (GitHub - fastlane/fastlane: 🚀 The easiest way to automate building and releasing your iOS and Android apps).

From our side, on the Xcode 8.3 stack you use there was no update since Xcode 8.3.3 so the most likely cause is a newer fastlane version or something in your code.

It seems you have the fastlane step on “update fastlane to the latest version”. This can be turned off if you want to. Related discussion: