RPC trips separate GFCI circuits on start up. Why?
George that is a soft start. This is a way to reduce the current on start up the common way is twin SCR’s that are pulsed on until the motor is at speed. This creates a large amount of harmonics that end up on the neutral and even the ground circuits. If you look at my original comment I thought that might be the case. Line reactors on the incoming line may be the best in this case, however RFI filters on the line side may also work but a good ground reference is needed for RFI filters , I have seen harmonics cause 20+ volts on the neutral and 13+ volts on grounds and this affects other circuits like you are experiencing. One way to see if this is the problem is to monitor the neutral to ground voltage when you start the system.  More than 2.5 volts in my experience not only causes GFCI problems but can cause switching power supplies like in computers and many lighting circuits to malfunction because the reference voltage is shifted. We see this in industrial facilities quite often and use line reactors mostly. 20 hp in a home based system is more than 2x anything I have ever seen and 4x normal homes in my experience.
Edit : whoops I thought it was 20 Hp not 20 amps. Still similar issues but a 1-2 hp motor may be able to be soft started without a line reactor but RFI filters may be the best option. I would suggest checking your homes grounding electrode system. Not that many years back a single water pipe feeding the home was totally code legal but with updates to plastic pipe some of these homes end up with insufficient grounds and the reason multiple grounding electrodes required today or supplemental ones.