Headlights problems of the 2018 Toyota Prius

Automatic high beams dim and then fail to brighten intermittently. When driving, automatic high beams function as intended then the dash indicator spontaneously turns off and the headlights fail to brighten. Vehicle has been to the dealership service department twice for this. The second time , the dealer was able to duplicate the problem both in my vehicle and in a 2019 Prius from the inventory. Toyota technical assistance is adamant that the problem is normal functionality. I fail to understand how the high beams not brightening when they should during night driving is normal functionality.