Canon 580 EXii problem

[nibbley-uk]

I have a 580 exii that has a problem with irregular flashing, i googled the problem and found most had issues with the hot shoe either a dirty pin or not a tight fit. But i have another 580 exii that works fine so borrowed the hot shoe from that one and still had the same issue, i then tried using off the camera with just triggers and same issue so tried lowering the power and it seem less irregular, but turned power to full and was getting many more missed flashes, anyone have a clue before it goes to repair shop ????

 

[LongLensPhotography]

batteries not full / worn out or corroded battery terminals? Maybe if some capacitor has failed it could do similar, but I am not sure if this is likely at all, no idea...

 

[nibbley-uk]

Definitely not batteries as used same batteries from the working 580. And terminals all look clean not sure what parts normally fail that provide the flash power.