Turn signals out on one side only, all bulbs are good

I have not consulted a schematic, so what I write may not be exact for your car.

Typically, the blinker unit is on the center switch pole, so it is toggled for left and right. So if it works for one side it should work for the other. However it needs lamp load to operate, poor connection may keep it from blinking. I also think the bulbs have two filaments, one for turn signals, the other for park/run lights. The ground is common for both. Loss of ground results in odd behavior. Have you checked both filaments?