Corrupted HTTP response

Hi

We are experiencing corrupted HTTP responses while consuming web-services. Our application do thousands of requests to a remote database; the requests are made with SOAP protocol and the result is an XML document. The channel is an unsecure HTTP transport. The application do the requests in keep-alive mode, so only one socket is opened for all requests.

This is what happens:

<s:Envelope xmlns:s="schemas.xmlsoap.org/.../"><s:Body><ExecuteQueryResponse xmlns="webservices.farmadati.it"><ExecuteQueryResult xmlns:a="schemas.datacontract.org/.../FDIWebServices" xmlns:i="www.w3.org/.../a:NumRecords><a:OutputValue>&lt; version="1.0" encoding="UTF-8"?&gt;&#xD;
&lt;TableResult&gt;&#xD;
&lt;Product&gt;&#xD;
&lt;FDI_T416&gt;034623278VF&lt;/FDI_T416&gt;&#xD;
&lt;FDI_T291&gt;034623278&lt;/FDI_T291&gt;&#xD;
&lt;FDI_T292&gt;VF&lt;/FDI_T292&gt;&#xD;
&lt;FDI_T293&gt;2007-03-06&lt;/FDI_T293&gt;&#xD;
&lt;FDI_T294&gt;R&lt;/FDI_T294&gt;&#xD;
&lt;FDI_T295&gt;GU&lt;/FDI_T295&gExecuteQueryResult></ExecuteQueryResponse></s:Body></s:Envelope>_T297&gt;2007&lt;/FDI_T297&gt;&#xD;
&lt;/Product&gt;&#xD;
&lt;/TableResult&gt;</a:OutputValue><a:Page>1</a:Page><a:RecordsPerPage>100</a:RecordsPerPage></ExecuteQueryResult></ExecuteQueryResponse></s:Body></s:Envelope>

Randomly last 64 bytes of the response are write in the middle of the message, corrupting the response.

The issue happens after hundreds of continuous request.

We think it's caused by Sophos because bypassing it, all works fine.

The corrupted messages has been taken at transport level, there is no transformation made by software. Server side there is a public IIS used by thousand of customers.

The software run on Windows 2016 with last service pack; Sophos XG is model 135 with firmware SFOS 17.1.1 MR-1.

We have already made an HTTP exception, disabled IPS, disabled AV, changed AV scanning model, tried all command line flags. Nothing.

Can anyone help us? Any suggestion?

Thank you for support

S.