We just purchased and plugged in a refurbished TCL 43” 4K Ultra HD Roku Smart LED TV (43S421) although the back says the model number is 43s423. The two are virtually the same.
We turned it on and the image has a shadow that slides up the screen, doubling anything on display. (I have a video but it won’t let me add it.) We double-checked the connections for the boards and tried some basic IT (off/on), factory reset of display settings. We’ve researched this problem best we can but haven’t found any viable solutions.
Simple answer: Entity that did the "refurbishment" merely repaired one of multiple issues (or else all they did was plug it in, attempt to power it up, see that it did so, and decide that it was working fine). Return it - for a refund, if at all possible, so that you can purchase your next one from a different business. A new one, if possible.