Sorry, just woke up.
Double picture issue is a clear cut failure of the TV's TCON board. It's found on the bottom center of the TV set, usually. Found on TV sets that have 100 or 200 Hz refresh rates. Dual picture is caused by the double frame rate processors on the TCON.
UN46D6900WFXZA is the US version of the TCON board -- we need to look at the Australian version, and there's usually a sticker found on the TCON which shows you your TCON's part number. I use this site to show and explain where to find that part number.
You see that sticker highlighted in PINK?
That's where you'll find your TCON's part number on your model.
Double click the picture on that site, and the picture enlarges. Remember...that's the USA version, not YOUR VERSION of the TCON. And they are correct about that warning..horizontal lines are rarely the TCON, but the DOUBLE PICTURE and video blanking and frozen picture are.
So...do we have 2 problems or just one related to the TCON. That's a question that should have been answered when you flexed the TV panel - Those lines should have disappeared at least, while the frozen screen/double images probably wouldn't have changed.
When you see those lines...grab the edges of your TV screen and rock it in opposite directions to flex the panel. Concentrate ONLY on the horizontal lines - see if they disappear or not. If they do...that's a bad panel. If they don't...more likely the TCON is causing ALL the symptoms.
You aren't afraid the remove the screws from the back cover are you?
To get to the TCON, you have to remove the stand, all the screws on the back, AND if the joystick button is on the back or bottom, there's usually a cable from that control to the TV's main board you have to release. When you take the rear cover off - move it up and peek under the cover. I usually just lift up and Feel the cable resisting during the lift.
Ok, that's enough information. Don't want information overload.
But I did find this on Gumtree, and I note that their stickers are slightly different, yet still useful. However that may be your model number with the proper version, OR it may be an ASIAN not Austrailian model.