@CPM posted:that is a 21w bulb on the taillight indicators
That is OK , and when into the front the wiring and bulbs are mounted as must be , try an other blinker relay .
But this isseu happens me also once , and I notice that the wiring on the front parking /turnsignal are switched .
to be sure check the front bulbs again , and check the wiring if they are on the right way connected and if like Julian say there is bad ground .
Also try this, parking lights on, ignition switch on and push the brake pedal (brake light), turn indicator on .
and look if all lamps are flashing
Simon