Garbage Collector Bug/WAD?

I think I am seeing a problem related to garbage collection. I am calling a function from my main event loop which initiates some async requests using this function:

function getImageAsync(port, file, url) 
    u = CreateObject("roUrlTransfer")
    u.SetMessagePort(port)
    u.setUrl(url)
    if not u.asyncGetToFile(file) then 
        print "getImageAsync() failed!"
    end if
    return u.GetIdentity()  
end function

I am always receiving event code=-10001 (Cancelled). I am able to get it to work by creating the roUrlTransfer objects in the calling function (and saving them in another object). This function now works...

function getImageAsync2(u, port, file, url) 
    u.SetMessagePort(port)
    u.setUrl(url)
    if not u.asyncGetToFile(file) then 
        print "getImageAsync() failed!"
    end if   
    return u.GetIdentity()   
end function

I've just started playing with BrightScript, but it appears the roUrlTransfer object is being freed when the function returns even though the request is active. Would this be expected behavior?