Originally posted by Ash I’ll reiterate, I know what I’m doing here, you can give me the benefit of the doubt on that.
But you must appreciate that you had to understand you were not necessarily conveying that impression ....
The only way to test P-TTL working, by isolating the flash exposure from all other possible influences, is to set M camera mode, set a fixed ISO, a fixed aperture, and a fixed shutter speed, and
report exactly what these are. These settings should be such that they completely eliminate all ambient exposure. We still don't have this assurance from your tests so far, as they have been in Av mode with who knows what Flash Sync mode setting, and what ambient exposure level is mixed in there.
I do of course accept that you appear to be dealing with some sort of flash contact or communication issue through the hotshoe, but that's still not absolutely proven by your reporting so far.
The other good thing to try is to use M flash mode on your flashes (again of course with every camera settings fixed to eliminate ambient light), in order to check if your flashes are syncing correctly. You can assess the flash exposure level on a series of shots in M mode as you progressively increase the power, say from 1/32th through to 1/2. At least this would prove whether its a flash contact issue, or if its likely to reside in software, ie the camera is not telling the flash what to output properly in P-TTL mode.