When I display both TSX and S-1 in SNAP 5 and SNAP 6, the longitude is flipped. It displays with the correct orientation, and the world view latitude is correct, but in the product viewer it displays the longitude backwards.
It seems to be only with certain scenes. I have had three people test it to see if they have the same issue, and it seems dependent on certain scenes.
The image below is a TerraSAR-X geocoded product after running the object detection function in SNAP 6.0.
As you can see from the land mask, the result is flipped horizontally.