1. Emergency flasher works with all 4 corner lights flashing.
2. Both left and right lights (frnt and back) work when blinkers are used.
3. Flasher relay must still be good in order for #1 and #2 to be working.

How do I stop the fast left blinker from occurring?

 

Sometimes a weak filament in a bulb or a bulb that's going bad can do this. I would rec changing them all out and go from there if all other electric switches are working properly.

 

Your brake bulb is out, se happened to me just replace and problem solved