sound like it should just be a harness issue... if it was the flasher, the rear turn signal shouldnt be working either.. it really sounds like it should just be the front bulb is out.

do you have a tow hitch? if so try removing the wiring for that. my turn signal was acting very strange and eventually wouldnt turn off. i cut the trailer wiring out and it was perfect, turns out the control module went bad, replaced it and all was well.

if it was me, i would first check all of my bulbs to make sure they were the right ones as well (single filament) then i would check all of the wires going to the bulbs on that side. especially where the wires snake behind the headlamp assemblies. its pretty easy to remove the front bumper if you have the proper torx bit (just dont touch the two torx bolts between the grill and headlights)