Correct me if I am wrong , but as long as C26 is still charged when you are taking resistance measurements across various points on the board, they will be affected by it? If C26 is still charged , then it is going to drive the transistors and slowly discharge as you are taking measurements. Even more true if the output is disconnected since there is no more load or anything else added to the circuit. As Quench stated there is nothing to cause capacitance on R56 to R54, his board doesn't measure that , but yours did..

You have the luxury of having a working board to take components and swap them. With so few components in the circuit, it should be a breeze to move the most probable components from one board to the other.

On the bad board picture , the zener hasn't been replaced yet ? Are you 100% sure of the polarity of that zener, verified with it's datasheet ? I know some manufacturers sometimes label the ANODE with a band on zeners.. you know , just to mess up people.

Does RT1 actually vary the voltage but it's just not high enough ? Or does it not vary the voltage at all ?

I would definitely try what wayout440 suggested as well , is that you should try to measure the voltage at all the components involved, like measuring your 95V at the R51 resistor directly , then checking to make sure it's still exactly 95V at the base of Q22 and at the collector of Q23, just to rule out a possible broken or damaged trace that would create resistance, changing the voltages.

Question to the smarter ones out there. If there really is 175V on R51 , then it would be burned open (looks good on the pic). But if it was open because it burned, how would Q22 actually get driven if the output is 97V. Could current leak through C27 and actually drive Q22 ? Like bad filtering on C26 letting AC ripple through , making Q22 act up and open / close very fast , lowering the expected voltage output ?