JAVA EWS item.load throws The request failed. Connection is still allocated

I hope anyone could help me. I'm building a web client email using the EWS Java API.

This is the code snippet that throws the exception:

if (mailList != null){
                for (Item item : mailList.getItems()){      
                    synchronized (item) {
                        es = Utils.initiateExchangeService(mailAccountData);
                        em = EmailMessage.bind(es, item.getId(), emPropSet);
                        item.load(new PropertySet(BasePropertySet.FirstClassProperties));

The line that throws the exception is:
item.load(new PropertySet(BasePropertySet.FirstClassProperties));

I know that this exception is usually get thrown while we use the same instance of the ExchangeService class, but not here.

appreciate any help