I had this problem, drove me mad for 9 months till I found the answer by accident.
The flash hazards function is fused on the same fuse as the headlight washer pump.
If your headlight washer pump goes faulty and causes the fuse to blow it takes out the flash function as well.
Have a look at fuse 2, satelite 1 above the main fuses below the steering wheel.
It's the row of 6 fuses you want number 2, second from the right 20A.
You may also have to un-plug the headlight washer pump and replace it in due cause.
Try your headlight washers first,if they work this is not the answer you want.
Hope this works for you.