If we replace RT with a Battery, then the voltage will distribute itself around the circuit.
Given that distribution, we will see no voltage differential at points A & B above.
Thus RX has no effect.. you can remove it... or replace it with a short.
RX has no effect on RT as shown above.
Now look again at the same technique applied below:
If we replace RT with a Battery, it should be obvious that there will be no differential between the Green Dots for the Bridge made of 1 ohm resistors and no differential between the Blue Dots for the Bridge made of 3 ohm resistors. Thus the Green Dots can be shorted with SB1 and the Blue Dots can be shorted with SB2. These shorts (SB1 & SB2) have no effect on RT. This places RB and RD in parallel as shown in the next diagram.
That is why your redraw is incorrect as you previously have shown.
Now solve for the Right Side Circuit and you will get the correct answer.