Xcode 10 Crash - device has no defaultDisplay

Upgrading to Xcode 10 has been pretty smooth apart from one issue. I'm unsure what causes it but the Simulator can constantly crash on startup with the error:

Device XXXX is available but has no defaultDisplay

Running this command fixed the crash loop for me:

sudo killall -9 com.apple.CoreSimulator.CoreSimulatorService

Thanks to this Stack Overflow post!