While using the API to publish a project to GroupShare using

var publishProjectResult = FileBasedProject.PublishProject(...);

the status response is "Failed".

If I then dig into the publishProjectResult.Messages I read the following...

Der Execution Server konnte das Projekt nicht veröffentlichen: Non-static method requires a target.. In de Log-Datei des Execution Servers finden Sie weitere Informationen.

So I then looked at the server's execution log where I find...

Sdl.StudioServer.Services.ProjectServer.PackagePublisher#Finished package publishing - error.
System.Reflection.TargetException: Non-static method requires a target.
   at System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target)
   at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
   at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
   at System.Data.Objects.ELinq.QueryParameterExpression.TryGetFieldOrPropertyValue(MemberExpression me, Object instance, Object& memberValue)
   at System.Data.Objects.ELinq.QueryParameterExpression.TryEvaluatePath(Expression expression, ConstantExpression& constantExpression)
   at System.Data.Objects.ELinq.QueryParameterExpression.EvaluateParameter(Object[] arguments)
   at System.Data.Objects.ELinq.ELinqQueryState.GetExecutionPlan(Nullable`1 forMergeOption)
   at System.Data.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
   at System.Data.Objects.ObjectQuery`1.System.Collections.Generic.IEnumerable<T>.GetEnumerator()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Sdl.StudioServer.Services.ProjectServer.PackagePublisher.Publish(Boolean useAssignment)

The same code has been working for ~18 months but this problem has happened twice in a very short period of time.