I have a 2007 fx4 and my passenger side bliker and brake dont work but bulb is good and is still illuminated when running with lights turned on, and when I plug my trailor lights in its opposite the drivers side trailor lights do it so I assume it could be a shotty trailor light harness?

Was wondering if anyone has run into this problem and if it is easily fixible or if its better to take it somewhere to get it fixed?