I don't know if it's normal, but compare all the numbers if you can.
My guess is that when you terminate the lease early, they use the difference between the lease balance (price - cap reduction - payments) and their estimated current vehicle value (Vehicle Value) to calculate the balance, and I assume that they're depreciating the current vehicle value by more than your monthly payment, so the payoff amount is increasing.
Seems like you need a different way out.