ODMAD DirSync Discovery Error: "An error occurred while updating the entries. See the inner exception for details" (4325082)

Discovery is failing with the following error:

Message = An error has occurred.
ExceptionMessage = An error occurred while updating the entries. See the inner exception for details.
ExceptionType = System.Data.Entity.Infrastructure.DbUpdateException
StackTrace =    at System.Data.Entity.Internal.InternalContext.SaveChanges()
   at CDS.Model.CDSDB.SaveChanges()
   at CDS.Model.EndpointSql.UpdateDomainControllers(ActiveDirectory existing, ICollection`1 updatedDcs)
   at CDS.Model.EndpointSql.UpdateActiveDirectory(ActiveDirectory updated)
   at BTCloud.Web.Areas.CDS.Controllers.AgentController.UpdateActiveDirectory(UpdateActiveDirectoryArgs arg)
InnerException = {
  ""Message"": ""An error has occurred."",
  ""ExceptionMessage"": ""An error occurred while updating the entries. See the inner exception for details."",
  ""ExceptionType"": ""System.Data.Entity.Core.UpdateException"",
  ""StackTrace"": ""   at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update()\r\n   at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction)\r\n   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)\r\n   at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesInternal(SaveOptions options, Boolean executeInExistingTransaction)\r\n   at System.Data.Entity.Internal.InternalContext.SaveChanges()"",
  ""InnerException"": {
    ""$id"": ""3"",
    ""$type"": ""S...