Just to add my experience, I have a 2017 with 6.5k miles. I have a voltage monitor on the battery. It has been sitting 5 days and the battery has 12.4 volts with the key off. So I will start it. I turn the key on and voltage drops to 12.1 volts - makes since with headlight. When I try to start it, the voltage drops to 11.9 volts (no lower) and the the starter starts making a clicking sounds maybe 2 times per second like the solenoid is trying to engage but cannot. I put it in gear and just shove it once so the engine breaks free. Then it starts right up and the voltage goes right to 14.1 volts and I am good for the rest of the day with no starting issues. I do not have to roll it to start it and it can be in gear with clutch in or neutral once I bump it loose - and I mean super easy bump. So if your bike acts up, do not panic and try that little trick to get you home at least.
Considering my experience and what you have all shared, I will propose a theory and maybe we can all consider if it makes any sense. Assume the starter on this bike as designed has an undersized or defective solenoid that drops out when the voltage falls below 12 volts - a starter solenoid should not drop out at near that high voltage in my opinion. Before the starter motor engages the voltage is above 12 and the solenoid engages, that pulls in the motor, but it drops below 12 when the motor pulls high amps, that draws down the voltage instantaneously, the solenoid disengages dropping out the starter motor as it should, the voltage rises above 12 under no load, and then it all repeats itself. We only hear a clicking a couple times per second as we hold the starter button.
A fresh battery could maintain a voltage over 12 volts even with the starter motor pulling, but a 2 year old plus battery is not likely to be able to do that even though it is still plenty strong enough to drive the starter - and should be good.
I propose there is a flaw in the starter solenoid design. You can overcome it with a new battery every couple years, but a battery should be able to last as long as it can hold the voltage above 10 amps under starter load and that might be 5-10 years if you maintain your battery. If that makes sense, and if many of you agree, maybe we can ask Kawasaki to make it right.
Please share your experience; buying a $50 dollar battery every two years is not a big deal. What is important is to understand the issue so we can manage it so it is only $50 every two years rather than several hundred dollars to the shop or worse a stranded bike.