Setup:

Umbraco Version: 7.4.3 Umbraco Forms: 4.3.2

Flexible load balancing

Some users in the lose their form security options. New ones are not an issue.

If I look at the console.log errors, I get this: )]}', {"Message":"An error has occurred.","ExceptionMessage":"Sequence contains more than one matching element","ExceptionType":"System.InvalidOperationException","StackTrace":" at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable1 source, Func2 predicate)\r\n at Umbraco.Forms.Web.Editors.FormSecurityController.GetByUserId(Int32 userId)\r\n at lambdamethod(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>cDisplayClass10.9(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Web.Http.Controllers.ApiControllerActionInvoker._1.MoveNext()"}

There is no other Sali in the list so not sure why it is saying "Sequence contains more than one matching element"