The 2017 kia optima is susceptible to some unusual brake light issues, aside from what is common with other vehicles. your firststep should always be to ensure that the bulb is good; it's quite possible that it's just burnt out. if it is, you may want to look to fuses or relays before you begin digging into more complex repairs. the '17 optima's connector pins can often get bent, which causes poor connection and failure to illuminate. you're also particularly susceptible to shorts in the brake light wiring system and wiring harness, so you should visually inspect the apparatus closely to see if this might be your issue. if you're unable to determine your point of failure through visual inspection and multimeter readings, you may want to have it checked out by a professional technician.
Brake lights flickering and dimming are issues in the 2017 kia optima.