Trying to identify the causes of success and failure, I built over 200 prototypes, using different designs and materials.
What I eventually realized, was that plastic film materials intended for printing cannot be used. The pre-treatments given to plastic for printing seem to cause adsorption of humidity from the air, giving them poor surface resistivity. I also discovered problems with insulating the generators with tape. My theory is that charges migrate through the tape adhesive, and build up there- creating a parasitic capacitance with the sectors that eventually stops the machine.
Using no insulating tape, and only insulating using polyester film, I started to get consistent results. I carefully designed the generator so that all the oppositely charged conductors are on opposing film surfaces, or have a large distance between them. These two things combined allowed the generator to be self-starting at up to 60% relative humidity, and with a "jump start", it will run at higher. I believe the power output can be increased significantly by encasing the sectors within the polyester, but this sort of manufacturing is beyond what I can do at my desk.