Problem with SOAP receiver

Hello,

Our PI system is 7.4 . We have a lot of interface with related to  proxy to soap.When they are used  very intensively, errors occur in soap receiver .

Types are error: 

503 server  not avalibale,

401 unauthorized ,

invalid content type for SOAP:TEXT/HTML  such as...

When system is restarted, mostly it is worked but after while again errors occur and a lot of message is waiting in queue.

what can we do for it?

Thanks in advance,

Nurhan