2013 Kawi 1700 Nomad starting issues

[Tim Earl]

2013 Kawi 1700 Nomad with 20,000 miles. It has a Cobra fi2000 module, Vance & Hines exhaust, and Kawi light bar has issues starting. I have a Bikemaster TruGel MG20Ch-BS battery that is less than two years old. When left on trickle charge, voltage reads 12.97. It will crank and run and the battery voltage holds at 14.8. The issue comes when the ignition is turned off and try to restart the bike. On second attempt, the voltage drops, and the starter struggles to turn, but the engine will start and I have experienced a backfire at this point. When attempting to crank it again, the starter barely turns and the voltage drops to around 8 or 9. I then have to recharge the battery.
The issue began two years ago with a different battery. I stopped to gas up after riding around 100 miles and the bike would not start. That is when the Bikemaster battery was installed.
I am assuming the stator is okay since it shows 14.8 volts when running, however I could be wrong. I have checked ground wires, unhooked extras added to the bike, etc.
Any help or advice is greatly appreciated.