Have you removed the torque converter lockup circuit's electrical connector from the rear of the transmission and cleaned and reseated it yet? This connector only has two connections so don't mistake it for the larger NSS (neutral safety switch) connector. You can use ordinary WD-40 to flush dirt/grease/ATF/etc. out of the connector's pins and female pin jacks. Simply shake or blow the excess WD-40 out of the connector when you're ready to reconnect it.
If that doesn't do it, then you can look at things like your TPS (throttle position sensor) and maybe even the temperature sensor. The lockup circuit is controlled by the PCM and it determines when to lock up your 32RH based on vehicle speed (speedometer cannot be intermittent), coolant temperature, and throttle position as indicated by the TPS. It is supposed to lock up at 35 mph with light throttle.
If you ever have an erratic idle or the engine does not rev smoothly as you step on the accelerator pedal, that might indicate a bad TPS.
If none of that indicates a problem, then it's time to get inside and check the torque converter control solenoid inside the transmission. I never needed to do that when I had that same transmission (32RH) but I have heard it can be a potential cause of that issue.