Trying to send information from %CSP.REST extended class to a Business Process

I've got a REST service that I can access via a browser. I can get it to take HTML tags as data and display it back to me (so I know the REST part is working). So if I send it this:

http://MyServer:57772/TestArea/rest/TestQuery?UUID=1&RTX=RTX123456&CareType=Palliative
 

Then I can pick out the data and tell it to display in the browser, which is great but what I really want to do is put the data into a string and send to a business process that will do lots of looking up but eventually return a URL that my REST service will then redirect the browser to.

Been trying to follow advice from here but something isn't working as all I get is ERROR #5002.

 /// TestArea's Dispatch class for all REST Services
Class REST.Dispatch Extends %CSP.REST
{ XData UrlMap [ XMLNamespace = "http://www.TestArea.com/urlmap" ]
{
<Routes>
<Route Url="/TestQuery" Method="GET" Call="TestQueryString" />
</Routes>
} ClassMethod TestQueryString() As %Status
{
Set tSC = $$$OK if 'tSC Quit tSC
Set tProxy = ##class(%ZEN.proxyObject).%New()
Set tProxy.UUID = $Get(%request.Data("UUID",1))
Set tProxy.RTX = $Get(%request.Data("RTX",1))
Set tProxy.CareType = $Get(%request.Data("CareType",1))

Set tTextOut = ##class(Ens.StringContainer).%New()
Set tTextOut = tProxy.UUID_"|"_tProxy.RTX_"|"_tProxy.CareType

// Need to create a temporary Service to use to call and get the response from
// our Business Process.

Set tSC = ##class(Ens.Director).CreateBusinessService("Strata JSON Service",.tService)

Set message = ##class(Ens.StringContainer).%New(tTextOut)
Set targetName = "StrataJSON2URLBP"
Set response1 = ##class(Ens.StringContainer).%New()
Set timeout = -1
Set description = "Strata URL"

Set tSC = tService.SendRequestSync(targetName, message, .response1, timeout, description)


Set %response.redirect = response1

Quit $$$OK
}

}

The Business Process StrataJSON2URLBP exists but is fairly sparse at the moment so I suppose the error could also be in there. Let me know if you want that posting.

The error response if that helps:

{
	"errors":[ {
			"code":5002,
			"domain":"%ObjectErrors",
			"error":"ERROR #5002: Cache error: <INVALID OREF>zTestQueryString+28^REST.Dispatch.1",
			"id":"CacheError",
			"params":["<INVALID OREF>zTestQueryString+28^REST.Dispatch.1"
			]
		}
	],
	"summary":"ERROR #5002: Cache error: <INVALID OREF>zTestQueryString+28^REST.Dispatch.1"
}