What causes the fixtures get dayburning? I think there a lot of causes for a fixture get dayburning, for example: Internal shorts, birds poop in the photocell, or the burning of the material of the photocell and gets black...

If your lanterns are group switched, I think that they are turned on on purpose for detecting lanterns with EOL lamps and relampping them.
If they are controlled by a timer switch, probably the time on/off are set wrong.
If they are controlled by a photo control, probably the photocontrol reached EOL.
Dusk and dawn lanterns with independent photo controls on top of them, are unique to English speaking markets such as the American and the British markets.

What causes the fixtures get dayburning? I think there a lot of causes for a fixture get dayburning, for example: Internal shorts, birds poop in the photocell, or the burning of the material of the photocell and gets black...

Birds poop seems severe, but it does not restrict the light so much it will do anything more than just shifting the switching time a bit. The light level difference between day and night is really several decades, the bird thing causes barely one decade attenuation...

Most frequent causes of the classic (non electronic) controls are burned relay (heater or coil, depends on if it is electromagnetic or thermal), bad contact on the photo resistor and mainly degradation of the photoresistor (it get quite hot, so its resistance increases over time till it gets completely open circuit; and open circuit is the same as darkness)