Check at the junction of r39 and r41, r41 and r40, the non-ground side of r33. Upstream of r34 should not be less than downstream, and the grid of V5b should be much more than 2mV signal. Discharge the caps, and check these points for DC resistance: Check resistance from V4 pin 2 to ground. It should read about 2M. Intensity pot wiper to ground, look for about 2.47M V4, pins 2 to 7, about 2M. You may also want to verify C25, C22, and C24 for value. The LFO signal is not making it to V5b in sufficient strength to allow that to half to work as designed, looks like. Now we try to find out why.