I am dealing with the same issue. I have not came across a valid solution yet. the stack trace is as follows:
 

Ifs.Fnd.FndSystemException: Server Error ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host. ---> System.Net.Sockets.SocketException: An existing connection was forcibly closed by the remote host

   at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)

   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   --- End of inner exception stack trace ---

   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   at System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count)

   at System.Net.Security._SslStream.StartFrameHeader(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)

   at System.Net.Security._SslStream.StartReading(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)

   at System.Net.Security._SslStream.ProcessRead(Byte[] buffer, Int32 offset, Int32 count, AsyncProtocolRequest asyncRequest)

   at System.Net.TlsStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   at System.Net.PooledStream.Read(Byte[] buffer, Int32 offset, Int32 size)

   at System.Net.Connection.SyncRead(HttpWebRequest request, Boolean userRetrievedStream, Boolean probeRead)

   --- End of inner exception stack trace ---

Server stack trace:

   at Ifs.Fnd.AccessProvider.FndConnection.CallGetResponse(String intface, String operation, FndRequestContext requestContext, FndManualDecisionCollection decisions, Byte[] requestHeaderBytes, Byte[] requestBodyBytes, FndApfAsyncInvoke asyncInvokeHandle, Boolean integrationGateway)

   at Ifs.Fnd.AccessProvider.FndConnection.AsyncGetResponse(String intface, String operation, FndRequestContext requestContext, FndManualDecisionCollection decisions, Byte[] requestHeaderBytes, Byte[] requestBodyBytes, FndApfAsyncInvoke asyncInvokeHandle, Boolean integrationGateway)

   at System.Runtime.Remoting.Messaging.StackBuilderSink._PrivateProcessMessage(IntPtr md, Object[] args, Object server, Object[]& outArgs)

   at System.Runtime.Remoting.Messaging.StackBuilderSink.AsyncProcessMessage(IMessage msg, IMessageSink replySink)

Exception rethrown at [0]:

   at System.Runtime.Remoting.Proxies.RealProxy.EndInvokeHelper(Message reqMsg, Boolean bProxyCase)

   at System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(Object NotUsed, MessageData& msgData)

   at Ifs.Fnd.AccessProvider.FndConnection.GetResponseDelegate.EndInvoke(IAsyncResult result)

   at Ifs.Fnd.AccessProvider.FndConnection.InvokeGetResponse(String intface, String operation, FndRequestContext requestContext, FndManualDecisionCollection decisions, Byte[] requestHeaderBytes, Byte[] requestBodyBytes, Boolean& abandoned, Boolean forcedSync, Boolean integrationGateway)

   at Ifs.Fnd.AccessProvider.FndConnection.InvokeInternal(Object requestBody, Object responseBody, String intface, String operation, FndRequestContext requestContext, FndManualDecisionCollection decisions, Boolean forcedSync, Boolean integrationGateway)

   --- End of inner exception stack trace ---

   at Ifs.Fnd.AccessProvider.FndConnection.InvokeInternal(Object requestBody, Object responseBody, String intface, String operation, FndRequestContext requestContext, FndManualDecisionCollection decisions, Boolean forcedSync, Boolean integrationGateway)

   at Ifs.Fnd.AccessProvider.FndConnection.InvokeInternal(String intface, String operation, Object requestBody, Object responseBody, FndRequestContext requestContext, Boolean forcedSync, Boolean integrationGateway)

   at Ifs.Fnd.AccessProvider.PLSQL.FndPLSQLCommandCollection.Invoke()

   at Ifs.Fnd.AccessProvider.PLSQL.FndPLSQLCommand.ExecuteNonQuery()

   at Ifs.Fnd.AccessProvider.PLSQL.FndPLSQLSelectCommandReader.Read(Boolean prepare)

   at Ifs.Fnd.Data.ADONetProvider.FndAPCommand.ExecuteDbDataReader(CommandBehavior behavior)

Hi all, Was any fix found for this? We are also facing the same issue on APP 9.