Took just one flash with me (430EX II) for my xmas trip and it flashes nicely. Photos, however, end up under exposed, because the flash flashes out of sync. It actually does not flash at all while the shutter does its thing, but maybe before that. I tried the flash with 2 bodies (5D3 & 6D) and the same thing happens with both. I did reset all settings etc. No luck.