Sorry, my english isn't very good
I have a problem with Af MA on my 1DX.
I respects the manual procedure for the MA settings but if I turn off the camera and turn on, the settings are cleared, reset to 0...
For exemple, with the EF 16-35 f2.8L II, in the first setting, the LCD screen displays  EF 16-35, I adjust W and T, I "wrote" the serial number (because the camera doesn't recognize the serial number) and it's OK.
I turn off the camera and turn on (lens always mounted on the camera)
And, in the first setting Af MA menu, the W and T values are 0 !
If I go in the sub menu with the INFO touch, my camera displays  EF 16-35...
The problem is identical with my EF 24-105 f4 L, EF 50, EF 70-200 f2.8 II and EF 40 f2.8 STM.
I specified my lens are not old. Purchased this year.
The CR2025 battery seems to work because hour/minutes/day are OK.
I have also a 5D Mark III and the Af MA works perfectly.
I have 2 friends who have a 1Dx et they don'have problem with Af MA.
I wrote to CPS today, this morning. I'm waiting a response.
Do you have same problems on your 1Dx ?
Thanks a lot for your help.From moderator: for workaround, see THIS POST