What we are seeing is that IRIS.WorkQueue globals are being defined for these calls but then the IRIS.WorkQueue is not being cleaned up and taking up large amounts of Memory.

You mention IRIS.WorkQueue globals consuming/using memory, but globals don't consume memory, they reside on disk.

I never seen any IRIS.WorkQueue globals, can you provide some detail?
What component is creating/using these globals?

You need to check the Storage defined in your class, typically automatically generated when the class is first compiled.

For example I have created a ConfigUtils.ConfigSettingsTable class:

Class ConfigUtils.ConfigSettingsTable Extends %Persistent
{

Property Name As %String;

Storage Default
{
<Data name="ConfigSettingsTableDefaultData">
<Value name="1">
<Value>%%CLASSNAME</Value>
</Value>
<Value name="2">
<Value>Name</Value>
</Value>
</Data>
<DataLocation>^ConfigUtils.ConfigSetti1ADBD</DataLocation>
<DefaultData>ConfigSettingsTableDefaultData</DefaultData>
<IdLocation>^ConfigUtils.ConfigSetti1ADBD</IdLocation>
<IndexLocation>^ConfigUtils.ConfigSetti1ADBI</IndexLocation>
<StreamLocation>^ConfigUtils.ConfigSetti1ADBS</StreamLocation>
<Type>%Storage.Persistent</Type>
}

}

In this case the globals used by my class are:

^ConfigUtils.ConfigSetti1ADBD (Data)
^ConfigUtils.ConfigSetti1ADBI (Indices)
^ConfigUtils.ConfigSetti1ADBS (Streams)
 

Instead of the 3 single globals, you can map ^ConfigUtils.ConfigSetti1ADB*

Note that you MUST check the actual global(s) name(s) used by your class.

If your class extends another persistent class, then the storage is defined in the superclass that define the extent (the first persistent class in class hierarchy).

To send JSON with an HTTP POST request using InterSystems ObjectScript, you can use the %Net.HttpRequest class. Here is a sample code snippet demonstrating how to do this:

Create an HTTP request object.
Set the server URL and other necessary properties.
Write the JSON payload to the request’s entity body.
Send the POST request.

Here is an example:

Set Body={}
Set Body.Name="John Smith"
Set Body.Address="ISC Dev community"
Set Body.SomeProperty="Some content"
Set Request = ##class(%Net.HttpRequest).%New()
Set Request.Server = "server"
Set Request.Location = "location"
Set Request.ContentType = "application/json"
// Convert the object to JSON and write it to the request's entity body
Do Body.%ToJSON(Request.EntityBody)

// Send the POST request
Set Status = Request.Post()

This is the expected behavior as documented in Message Contents

Management Portal displays only the first 20000 characters of the message by default, this can be changed as documented in Changing the Character Limit for XML Messages in the Contents Tab

So, in your case for only EnsLib.HTTP.GenericMessage you can:

Set ^EnsPortal.Settings("All","MessageContents","OutputSizeLimit","EnsLib.HTTP.GenericMessage")=<whatever size you feel appropriate>

or for any class:

Set ^EnsPortal.Settings("All","MessageContents","OutputSizeLimit")=<whatever size you feel appropriate>

Using your code (simplified by me) from terminal it works fine using a sample CCDA from here.

set ccdaStream = ##class(%Stream.FileBinary).%OpenId("c:\temp\CCDA_CCD_b1_Ambulatory_v2.xml")
write "Size of CCDA Stream: ", ccdaStream.Size,!
set xsltTransform = "SDA3/CCDA-to-SDA.xsl"
set tTransformer = ##class(HS.Util.XSLTTransformer).%New()
set tSC = tTransformer.Transform(ccdaStream, xsltTransform, .sdaStream)
if 'tSC write "Transformation to SDA3 failed with error ",$system.Status.GetErrorText(tSC),!
set fhirStream = ##class(%Stream.TmpBinary).%New()
set SDA3ToFHIRObject = ##class(HS.FHIR.DTL.Util.API.Transform.SDA3ToFHIR).TransformStream(sdaStream, "HS.SDA3.Container", "R4")
if '$isobject(SDA3ToFHIRObject.bundle) write "Failed to transform SDA3 to FHIR",!
do SDA3ToFHIRObject.bundle.%ToJSON()

The result/output is a pretty long JSON FHIR bundle with CCDA data (I didn't check the content!)

Does your code works with that sample CCDA?

If not, then maybe there is something wrong in your CCDA.

For my test I used: IRIS for Windows (x86-64) 2024.1 (Build 267_2U) Tue Apr 30 2024 16:35:10 EDT