ActionReturn entities not setting encoding for large binary entities reliably

I have a custom entity that returns binary as it's requesting an image, but could be any resource.

I am using the ActionReturn object to return my OutputSteam of bytes:
eg:
ActionReturn actionReturn = new ActionReturn("BASE64", "image/jpeg", out);

When I made a request for this entity, for large resources, the encoded binary is displayed on screen. Inspecting the response headers has this:
Content-Type:text/html;charset=UTF-8

ie its ignoring my encoding and mimetype.

However for smaller resources, it is working correctly, the image displays as an image, and the headers correctly show:
Content-Type:image/jpeg;charset=BASE64

After investigating EntityActionsManager.java and LazyResponseOutputStream.java and adding a bunch of println statements everywhere, I get this:

Thumbnail:
resource.getMimeType(): image/jpeg
resource.getLength(): 3050
actionReturn.encoding: BASE64
actionReturn.mimeType: image/jpeg
not null, setting inputs into response...
response.isCommitted.1: false
//SETTERS HERE

response.isCommitted.2: false
response.getCharacterEncoding: BASE64
response.getContentType: image/jpeg;charset=BASE64
response.isCommitted.3: false

actionReturn.encoding: BASE64
actionReturn.mimeType: image/jpeg
response.getCharacterEncoding: BASE64
response.getContentType: image/jpeg;charset=BASE64

Larger image:
resource.getMimeType(): image/jpeg
resource.getLength(): 33328
actionReturn.encoding: BASE64
actionReturn.mimeType: image/jpeg
not null, setting inputs into response...
response.isCommitted.1: true
// SETTERS HERE

response.isCommitted.2: true
response.getCharacterEncoding: UTF-8
response.getContentType: text/html;charset=UTF-8
response.isCommitted.3: true

actionReturn.encoding: BASE64
actionReturn.mimeType: image/jpeg
response.getCharacterEncoding: UTF-8
response.getContentType: text/html;charset=UTF-8

In the above output, the SETTERS HERE is where EntityActionsManager sets the supplied values into the response. In some cases, the response is already committed, so it will do nothing. actionReturn still has the right info, but it can't set it into the response.

It may be due to this:
http://java.sun.com/j2ee/1.4/docs/api/javax/servlet/ServletResponse.html#setCharacterEncoding(java.lang.String)
This method can be called repeatedly to change the character encoding. This method has no effect if it is called after getWriter has been called or after the response has been committed.

Could it be in LazyResponseOutputStream ?

Also, when it works the content length was 3050 because I requested a thumbnail of the image as the entity, when it fails the contentLength was 33328. Both image/jpeg and both BASE64.

Discussed with Aaron over email. Hopefully this captures it all in one post.