Why does my output stage rectify when I use a preceding stage?
There are two problems: 

1) The first stage can only work properly at base voltages below zero. When the collector-base junction is reverse-biased, i.e. in normal operation mode, the the total voltage drop on R67 and R62 equals that on R56 (there is a small difference, which we can ignore here). This value can't be more than about 11 V, as the total voltage drop on all of these resistors, diodes and the transistor is 24 V. When when the base voltage is anywhere from slightly below zero to positive, the collector doesn't have anywhere to go, so to speak, it cuts off. 

2) floating input, and we don't know anything about your source.

You may want to use an emitter follower with a diode bias, or two emitter followers in series, npn and pnp.