Event source based emails

We are looking at improving UX through ticket logged emails base on source; e.g., 'We have logged a ticket following your call to our Support Analysts' when logged with the source of 'Phone'.

We have successfully implanted this when using the system defined source options using the code below...

ADDITIONAL VARIABLE
[AV_SOURCE_TYPE"] = "event.receiveSourceType",


ACTION PROCESSOR RULE
{

        [[ Internal User - Logged Email - Self-serviced by Portal]],

        [[

            ACT_TYPE_SC == "ASSIGN"

                and (tonumber(ACT_TYPE_COUNT) == 1)

                and (EVENT_TYPE == "i"

                    or EVENT_TYPE == "s")

                and (AV_REPORTING_USER_SC == AV_AFFECTED_USER_SC

                    or AV_REPORTING_USER_SC == "")

                and (AV_AFFECTED_USER_SC or "") ~= ""

                and AV_AFFECTED_USER_SC ~= "XXEXTERNAL USER"

                and AV_SOURCE_TYPE == "assystnet"

                and (tonumber(AV_BUNDLE_EVENT_ID) == 0)

        ]],

        strSendMailV2 .. "TEMPLATE=SM_INTERNAL_CALL_LOGGED RECIPIENTS=TO_AFFECTED,CC_REPORTING",  

        "stop"

    },

However, we have trouble using this method when using user defined (1-18) source types. The additional variables output a question mark (?) in all instances tried. We have also tried using event.receiveSourceTypeEnum so we can define by the integer value but receive 'unsupported_type' instead.

Any suggestions or guidance would be appreciated. We have opened a support ticket and will post here if we get an answer there first.