I have this exact same problem. Mine is intermittent. sometimes it works.
I replaced my ignition switch about a year ago. I've pulled the combination flasher and it is ok. It is simply intermittent.
from teh diagram of tehe multifuntion switch there is a connection that connects ground to teh flasher. I believe that that is intermittent as when it is acting up, i get no indicator lights at all. 4 ways, left, right, dash.
One thing though from teh diagram of the internals of the mutifuntion, that ground conenction appears to be only on when 4ways are on. but if that were true the flasher relay would be on all the time so i think that may be misleading.
can anyone confirm?