That can happen when there is a bad ground to one of the lights.
turn signal relay fuse
If the lights blink fast on either side of the car then this means you either have non-factory bulbs in the car or you need to replace your blinkers because one of your lights is out.
your rear bulb is blown - replace the bulb The turn signal blinks fast because the bulb is going out. That is also why the others dont blink.
turn signal relay is bad
Buy a "highway" turn signal flasher
Check your bulbs and your flasher.
You could be hitting the flash feature on the turn signal arm when you use it.
Probably needs a fuse.
This may very well be a problem with your ground connections at that turn signal.
Why would you want the blinker faster. They should blink at factory specs.
none unless you put it on check for a bad ground connection in the headlight/signal wiring.
The headlamp switch is on the turn signal stalk.