Mobile Center is Xamarin Build is failing with pthread_mutex_lock error

Question

I'm building a Xamarin.Forms app into Xamarin.Android using Visual Studio App Center. The app builds fine in develop and release configurations on my machine, but when I try to build on Mobile Center, the build almost completes (i.e. the MSBuild stage), but then I get this fatal error:

mono_os_mutex_lock: pthread_mutex_lock failed with "Invalid argument" (22) ##[error]Error: /Library/Frameworks/Mono.framework/Versions/5/bin/msbuild failed with return code: null

Answer 1

Ah, Nuget problems!

I'm using Fody and PropertyChanged.Fody to implement my IOnPropertyChanged interfaces and events.

I was explicitly referencing version 2.0.1 of PropertyChanged.Fody and and 2.1.2 of Fody. I saw a reference to netstandard in a non-fatal message in the build logs. Mobile Center doesn't support NetStandard (yet)

So, I updated Fody to the latest stable version 2.1.4, while PropertyChanged.Fody remained at the same version. Now the build completes, woo!