HazelcastSerializationException is thrown when doing operations in parallel

[alparslanavci]

When running a test which loads data in parallel, the following exception is thrown:

System.AggregateException : One or more errors occurred.

----> Hazelcast.IO.Serialization.HazelcastSerializationException : Class-id: 106 is already registered!

at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)

at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)

at System.Threading.Tasks.Parallel.ForWorker[TLocal](Int32 fromInclusive, Int32 toExclusive, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Func`4 bodyWithLocal, Func`1 localInit, Action`1 localFinally)

at System.Threading.Tasks.Parallel.ForEachWorker[TSource,TLocal](IEnumerable`1 source, ParallelOptions parallelOptions, Action`1 body, Action`2 bodyWithState, Action`3 bodyWithStateAndIndex, Func`4 bodyWithStateAndLocal, Func`5 bodyWithEverything, Func`1 localInit, Action`1 localFinally)

at System.Threading.Tasks.Parallel.ForEach[TSource](IEnumerable`1 source, Action`1 body)

--HazelcastSerializationException

at Hazelcast.IO.Serialization.SerializationService.ToObject[T](Object object)

at Hazelcast.Client.Proxy.ClientMapProxy`2.Get(Object key)

When it is changed the parallel client down to be single threaded this issue does not arise.