RestSharp latest version breaks my API's post method (add Guid before and after the body)

Question

Since latest version of RestSharp, all my post API's are failing because something has been added to the bodies I send.

Looks like a Guid id is generated and is added before and after the body for each call; the issue is it's not accepted by all my API's providers.

FYI, I created 2 identical console apps, one with version "106.12.0", and one with latest version "107.3.0". please see below the result:

Thanks in advance to help me with this BR -Vince

Examples:

Working with Version="106.12.0" : before:

Content-Type: text/plain; charset=utf-8
Content-Disposition: form-data; name="application/xml"
  <SMSBoxXMLRequest>
  <username>cnoxxxx</username>
  <!-- password hidden -->
  <command>WEBSEND</command>
  <parameters>
    <service>VALAIS</service>
    <text>Test de Message Sms 1</text>
    <test></test>
    <receiver>+4177222333444</receiver>
  </parameters>
</SMSBoxXMLRequest>

after: Not Working with Version="107.3.0" :

**--497993c6-3ef7-47fb-b527-403c1eefedf8**
Content-Type: text/plain; charset=utf-8
Content-Disposition: form-data; name="application/xml"
  <SMSBoxXMLRequest>
  <username>cnoxxxx</username>
  <!-- password hidden -->
  <command>WEBSEND</command>
  <parameters>
    <service>VALAIS</service>
    <text>Test de Message Sms 1</text>
    <test></test>
    <receiver>+4177222333444</receiver>
  </parameters>
</SMSBoxXMLRequest>
**--497993c6-3ef7-47fb-b527-403c1eefedf8--**


**--3277a8db-bd83-4f3c-af2e-d34efe76fe98**
Content-Type: text/plain; charset=utf-8
Content-Disposition: form-data; name="application/xml"
  <SMSBoxXMLRequest>
  <username>cnoxxxx</username>
  <!-- password hidden -->
  <command>WEBSEND</command>
  <parameters>
    <service>VALAIS</service>
    <text>Test de Message Sms 2</text>
    <test></test>
    <receiver>+4177222333444</receiver>
  </parameters>
</SMSBoxXMLRequest>
**--3277a8db-bd83-4f3c-af2e-d34efe76fe98--**


**--5b81fa95-a0b9-4f5c-9242-742734b0241e**
Content-Type: text/plain; charset=utf-8
Content-Disposition: form-data; name="application/xml"
  <SMSBoxXMLRequest>
  <username>cnoxxxx</username>
  <!-- password hidden -->
  <command>WEBSEND</command>
  <parameters>
    <service>VALAIS</service>
    <text>Test de Message Sms 3</text>
    <test></test>
    <receiver>+4177222333444</receiver>
  </parameters>
</SMSBoxXMLRequest>
**--5b81fa95-a0b9-4f5c-9242-742734b0241e-**-