There is an error in the rdplex.cpp code for handling technology transfer to the Titan rocket. The code (lines 1528-35 per commit 062828f) at the end of the case reads:

    if ((n1 >= 75 || n5 >= 75) && (n3 >= 75 || n4 >= 75))  // Tech      from multiple programs
        //old code: Data->P[player_index].Rocket[ROCKET_HW_TWO_STAGE].Safety = 65;

    {
        break;
    }

case ROCKET_HW_THREE_STAGE:    // Saturn/N1

This needs to be corrected. The section labeled "old code' should be executed in the if... statement, because it's the right code and in line with the other rocket tech transfers. The break statement should be moved to after the if... statement, so execution won't continue into the ROCKET_HW_THREE_STAGE case.

This is a straightforward change, but I'm working on another issue at the moment. I'll try to get back to this one asap.