The "LinkAssemblies" task failed unexpectedly

I updated all packages in my project and now I get this error with Linker enabled:
looks like an old bug: https://bugzilla.xamarin.com/show_bug.cgi?id=57645

        Xamarin.Android.Common.targets(1696,5): error MSB4018: System.NullReferenceException: Object reference not set to an instance of an object
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.TypeReferenceExtensions+<GetMethods>d__4.MoveNext () [0x00038] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.TryMatchMethod (Mono.Cecil.TypeReference type, Mono.Cecil.MethodDefinition method) [0x00027] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.GetBaseMethodInTypeHierarchy (Mono.Cecil.TypeDefinition type, Mono.Cecil.MethodDefinition method) [0x00009] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.GetBaseMethodInTypeHierarchy (Mono.Cecil.MethodDefinition method) [0x00006] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.MapVirtualBaseMethod (Mono.Cecil.MethodDefinition method) [0x00000] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.MapVirtualMethod (Mono.Cecil.MethodDefinition method) [0x00000] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.MapVirtualMethods (Mono.Cecil.TypeDefinition type) [0x00027] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.MapType (Mono.Cecil.TypeDefinition type) [0x00000] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.MapType (Mono.Cecil.TypeDefinition type) [0x0002d] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.TypeMapStep.ProcessAssembly (Mono.Cecil.AssemblyDefinition assembly) [0x0001b] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Steps.BaseStep.Process (Mono.Linker.LinkContext context) [0x00025] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Mono.Linker.Pipeline.Process (Mono.Linker.LinkContext context) [0x0001b] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at MonoDroid.Tuner.Linker.Run (Mono.Linker.Pipeline pipeline, Mono.Linker.LinkContext context) [0x00000] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at MonoDroid.Tuner.Linker.Process (MonoDroid.Tuner.LinkerOptions options, Mono.Linker.LinkContext& context) [0x00070] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Xamarin.Android.Tasks.LinkAssemblies.Execute (Java.Interop.Tools.Cecil.DirectoryAssemblyResolver res) [0x002c8] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Xamarin.Android.Tasks.LinkAssemblies.Execute () [0x001fa] in <a9f581d0c2a2409a88d42cf1050f6508>:0
        Xamarin.Android.Common.targets(1696,5): error MSB4018:   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute () [0x00023] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/msbuild-15.4/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs:631

And after turning of the linker I get this:

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets(3,3): Error: error XA4212: Type Android.Support.V4.App.JobIntentService/JobServiceEngineImpl implements Android.Runtime.IJavaObject but does not inherit Java.Lang.Object or Java.Lang.Throwable. This is not supported.

Running the latest stable xamarin studio and android versions.

Suggestions are welcome.

Building and linking was working before the update.