Since the headphone connector is on the left, the right cable is getting more strain.  It's always breaking in the knot.  The decision was made to swap the playback channels in software & wear the phones backwards to spread the strain.   It's unlikely anyone else in the world has resorted to such drastic action to keep 38 year old phones alive.

Also tweeked the reverb again.  It seems to cut completely off when reverb_level2 goes below -50.   It could be a quantization problem with float32.