The date header format may not correct. According to RFC3261, the date hearder should be:
The Date header field contains the date and ime. Unlike HTTP/1.1, SIP only supports the most recent RFC 1123 formate for dates. As in [H3.3], SIP restricts the time zone in SIP-date to "GMT", while RFC 1123 alows any time zone. An RFC 1123 dte is case-sensitive.
The Date header field reflects the time when the request or response is first sent.
The Date header field can be used by simple end systems without a battery-backed clock to acquire a notion of current time. However, in its GMT form, it requires cients to know their offset from GMT.
Example: Date: Sat, 13 Nov 2010 23:29:00 GMT
If the Date header is not correct, there are two ways to overcome this:
1. Correct the DUT's Date header format
2. Since the header is not really used by Aacus SIP end point, you may use a filter to filter it out in Protocol development/Incoming filters.