Hi,
Two weeks ago i had to repair my left one, after disassembling the pedal completely and comparing to the right one, i saw that the spring (located in the outer edge, inside the pedal) was slightly more open, and it will loosen and detach from the secure hole, when you try to attach your foot on, or rotate the clip by hand...
So with the help of 2 pliers i made it. But not without stripping a piece of meat from my fingers... i did it at home without proper tools, and it took me to 2 days to repair it to the point that now it is even better than the right pedal. Maybe next time i have to open them to lube i check the right one.
I recommend securing the spring in a vise so you will not hurt yourself! and then with the help of a very good set of pliers closing the spring a bit by twisting the extremity of the spring in a spiral way. After some trial and error it is possible.
The difficult part is securing the spring so you can work on it.
Good luck!
Regards