sqr wave generator

This is an implementation of an analog function generator. We first create a voltage controlled oscillator (VCO) which outputs a triangle wave. Integrated into the VCO is an opamp setup to be a comparator which outputs a square wave. The triangle wave is then shifted to be centered at 0 and then diode shaped to create a sine wave. At the moment, the sine wave is correctly shaped on the rising edge but there's an issue on the falling edge. Anyone have any recommendations for a fix?