Most likely the problem is caused by the part as described above. But if that doesn’t pan out, could be a defective switch that you use to turn it on or the bulbs it illuminates have a bad connection. If replcing the flasher unit doesn’t work, you might try just removing and reinstalling all the bulbs that are supposed to be flashing, see if that helps. The flashing function works by measuring the amount of current going to the bulb, so a bad connection anywhere in the circuit reduces the current & fouls that up. Likewise, replacing a burned out bulb with a low curent LED version can cause this. A defective switch can sometimes be revived by a spray in the appropriate spot with contact cleaner.