Incredible!   I really missed something important!
@Dan Pasco    Thanks for the pointer. I never stop learning.

Another unknown feature that isn't mentioned anywhere else.

Ah! csp.pagename.CLS

THX

No legal that I know of

What do you mean by csp.INT  ?? 

StreamPrefetch looks related but it is totally related to the .NET end (googled SQL prefetch in .NET), 
while <INVALID OREF> is clearly an issue @Ensemble end.
I'm not too deep in the external ODBC  world but I assume that collecting the resultset and
transmitting it to .NET  [ %SYS.SQLStreamSRV ] could happen asynchronously in different processes.
So I doubted %Stream.TempCharacter which is bound to a process private Global  vs. a standard Global visible also to other processes. And only the final %Save nails it down.
I wonder if you experience the same problem if you run your query from
terminal prompt: do $system.SQL.Shell()  
This can signal if the ODBC connection plays a role at all.

Jeff,
if this is still happening I suggest contacting WRC. 
They have access to the sources and more diagnostic tools.

%SYS.SQLStreamSRV.obj  is a deployed routine / class so we can't look into its details.
<INVALID OREF> expects a (stream) Object, but it doesn't exist.
So an additional check might be required.  Or you force some content for testing.
 

ClassMethod GetHL7Msg(pId As %String) As %Stream.TmpCharacter [ SqlName = GetMsg, SqlProc ]
{
    Set tHl7 = ##class(EnsLib.HL7.Message).%OpenId(pId,,.tSC)
    Throw:$$$ISERR(tSC) ..GetErr(-400, "HL7 Message with ID "_pId_" Not Found.")
    Set tMsg = ##class(%Stream.GlobalCharacter).%New()
    Set tSC = tHl7.OutputToLibraryStream(.tMsg)

     ;;  Throw:$$$ISERR(tSC) ..GetErr(-400, "HL7 Message with ID "_pId_" failed.") 
         IF 'tMsg.Size DO tMsg.Write("*** no message for ID:"-pId_" ***")
         SET tSC=tMsg.%Save()

    Do tHl7.%Close()
    Return tMsg
}

So you should have always a Stream Object

So my next try would be to add %Save  of the Stream Object before closing  tHl7

ClassMethod GetHL7Msg(pId As %String) As %Stream.TmpCharacter [ SqlName = GetMsg, SqlProc ]
{
    Set tHl7 = ##class(EnsLib.HL7.Message).%OpenId(pId,,.tSC)
    Throw:$$$ISERR(tSC) ..GetErr(-400, "HL7 Message with ID "_pId_" Not Found.")
    Set tMsg = ##class(%Stream.GlobalCharacter).%New()
    Set tSC = tHl7.OutputToLibraryStream(.tMsg)

        IF tSC SET tSC=tMsg.%Save()          

    Do tHl7.%Close()
    Return tMsg
}

pure COS solution, split into  steps to allow comments (you may condense it of course)

read  arg    ; get something to work on
"Not  Working Example":"x, y, z, a, b, c",

set name=$piece(arg,":",1)   ; split name from content
set content=$piece(arg,":",2)
if $extract(content,1)=""""  {    ; we got a quuted list
           set value=$piece(content,"""",2)    ;extract first quoted
           set value=$piece(value,",",first,last)  ; pick the relevant pieces
          }
else  {  
       set value=content            ;  no quotes, no pieces
}

 

Hi  @Dan Pahnke 
The "Red Fire Button"  is a synonym I used over the years with my various teams for an action/decision
that should not be taken by a single person but follows (at least) the 4-eyes-principle.

Inspired by an endless number of Airforce fighting movies from Hollywood and
the old but still incredible song from The Dubliners.
And its best cover version

BINGO !