When dusk to dawn lights flicker it's usually caused by a by dusk to dawn switch which is known as a photocell.
Eventually overtime the photocell switch that detects the dark and light and turns the light on and off goes bad after so many on and off cycles.
Then that can lead to the dusk to dawn lights flickering.
Another cause is the bulb has come loose in the dusk to dawn light or there might be some bugs or other dirt etc in the sockets of the dusk to dawn light.
If you can do so remove the bulbs after turning off the power and look into the sockets and see if there are any dirt or other debri such as bugs in the sockets.
Sometimes on my dusk to dawn lights that use those flood light bulbs that screw in they will have some bugs that get into the sockets which causes the dusk to dawn lights to flicker.
Or you could have some loose wiring that leads to the dusk to dawn light.