I doubt a bent bellcrank as those are pretty beefy. I've had the cable slip off the rocker thingy and then the rocker thingy get messed up. Sounds like your bellcranks are sticky too.
aluminum and steel and water...nasty mix
that design was poor and the usual culprit of bad ebrake situations in places that get rain or snow...
The 1st time I cleaned,oiled and adjusted them ,all was fine.
Then when they started to jam again 12 months later, cleaning and oiling made no difference this time.
The bellcranks seem to move freely when you disconnect the cable and operate them by hand but my hands cant pull on them as tight as the cable can.
I was wondering if they are worn and moving slightly sideways or twisting when the cable pulls them.
Hopefully all will be revealed when I pull them apart this time