EAV = Early Adopter Victim.

I love my 1D X - responsive as heck, great high ISO performance, a joy to use. Except.....

In the AFMA menu, when When Adjust by Lens is selected, powering off then on resets the setting (or W/T settings for a zoom lens) to zero, and also clears out a manually entered lens serial number. If I set it to All by Same Amount, the setting entered is retained...but, powering off actually changes the setting to Adjust by Lens, which is zeroed out. Even setting it to Disable and power cycling results in it being set to Adjust by Lens.

The same reversions occur if the camera goes into standby mode - when it's woken up, the AFMA setting, regardless of where it was left, reverts to Adjust by Lens with the previously set value(s) zeroed out.

This occurs with several lenses (zooms and primes), and occurs in any mode (standard modes as well as the C1-C3 user settings).

I called Canon Tech Support, who said it definitely should not do that (duh) but had no solution for the issue. (I was asked, "Ummm, I hate to ask, but you did press Set after entering the value, right?") The tech rep indicated that he tried it on a 1D X and it didn't display that behavior. At least one other person (who posted on CR) has the issue.

I expect a forthcoming firmware update which, "Addresses an intermittent issue that..." I can't see how it can be anything but a firmware issue, and I would bet it's a bug triggered by other settings (e.g., people who enabled the C2 and C3 settings before applying AFMA see the problem, or some other odd combination).

B&H support stated that Canon has informed them of a forthcoming firmware update to address the issue.