I covered an event today with my Canon 7D and YN568EX when all of a sudden the flash changed from manual to E-TTL mode. I tried switching it back to manual using the in camera flash menu and speedlight mode button but that proved ineffective; It goes back to E-TTL mode every time I try to change it to manual. In addition, it won't enter manual mode even when the flash is not on the camera's hot shoe. Other than that, the flash is working fine.
Has anyone experienced this issue with theirs? What can I do about this?
I had this same problem, and I needed to go into my camera's speedlight control / flash function menu to alter the flash settings. This is REQUIRED if you are using the Yongnuo YN622 transceivers, and if you are using two or more, then you need to activate the Flash Group to A:B or A:B:C so that you can control them separately (obviously putting each of the YN622's on its own group).
It sounds like something in the flash unit has gotten stuck in E-TTL mode. The only thing I might suggest is removing the batteries for a few minutes to see if that allows the unit to reset. Also try setting all the options to the original default settings. If that doesn't work you may have to decide whether to try and get it repaired or just replace it. It would probably cost less to just replace it.