Failing to set extended properties via EWS

-----MAPI property of the MSG----
Type: PT_LONG
DASL: http://schemas.microsoft.com/mapi/id/{00062003-0000-0000-C000-000000000046}/812A0003
Named Prop Name: id: 0x812A=33066 = PidLidTaskAcceptanceState, dispidTaskDelegValue
Named Prop Guid: {00062003-0000-0000-C000-000000000046} = PSETID_Task
Value: 0

-----code----
new EmailMessage(...);
...
ExtendedPropertyDefinition def = new ExtendedPropertyDefinition(new Guid("00062003-0000-0000-c000-000000000046"), 0x0000812A, MapiPropertyType.Integer);
msg.SetExtendedProperty(def, 0);
...
msg.Save(...);

Microsoft.Exchange.WebServices.dll version 14.2.51.0

-----error----
      <m:CreateAttachmentResponse xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages" xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types">
        <m:ResponseMessages>
          <m:CreateAttachmentResponseMessage ResponseClass="Error">
            <m:MessageText>The extended property value is inconsistent with its type.</m:MessageText>
            <m:ResponseCode>ErrorInvalidExtendedPropertyValue</m:ResponseCode>
            <m:DescriptiveLinkKey>0</m:DescriptiveLinkKey>
            <m:MessageXml>
              <t:ExtendedFieldURI DistinguishedPropertySetId="Task" PropertyId="33066" PropertyType="Integer" />
            </m:MessageXml>
            <m:Attachments />
          </m:CreateAttachmentResponseMessage>
        </m:ResponseMessages>
      </m:CreateAttachmentResponse>

----observation----
Strangely enough, another similar property is successfully set, for example 0x00008129.
The same property is easily edited via MAPI.