We have established some level of resolution . By holding down the C Fn. on the ex600 we can reset to ETTL. (The flash unit for some unknown reason has been switching to TTL which produces a full power (maximum) flash - hence the massive overexposure...
We've had this happen with at least 2 cameras - one was a new one that we recently bought because we thought the older Mk-iii was faulty. So in fact it's happening on Mk-iii bodies and Mk-iv bodies - perhaps the flash is at fault? - again we've tried...
We are experiencing the same problem i.e. shooting the same subject in the same lighting - some shots are OK but others are grossly overexposed. we're working in a childrens medical setting and can't afford not to have confidence in our equipment.
