Hi, I have a workhorse old 5D Mark III and have noticed recently that the ISO button is proving to be less and less reliable. After pressing it, rather than always staying down for a couple of seconds so that the ISO setting can be changed, sometimes it releases itself instantly meaning that I end up changing the shutter speed instead - or alternatively have to hold the ISO button down at the same time as turning the wheel (which is incredibly tricky when adapting to changing light - I'm a live music photographer).
Sometimes it does work fine, which is in its own way just as frustrating, as you never quite know what's going to happen.
Is there a simple fix for this?
