Firmware Updates and Micro-adjustments

I was just reading Robert's comment about the firmware updates for the 5DIII. There is a remote possibility I might use a 300mm/2.8 and a 2X TE but am hesitant to update.
Several years ago I updated the firmware for a 50D. The update screwed up all of the micro adjustments I had done. I have not done any updates since.

I am wondering the micro-adjust issue was a one of instance, or if it is typical of doing firm ware updates?

Thanks.

updating 5D3 firmware does not affect stored MA values. you can also back up these values to your PC before updating using EOS viewer utility

Thanks Arash. It was not that I lost the MA values for the 50D; it is that something changed. The original values were still stored in the camera but were no longer accurate. I had to redo the MA's for whichever lenses I had at the time. I remember cluing in to the issue at the time because of comments on DP Review. It sounds like you have done camera firmware updates with no change in focus accuracy.

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Originally Posted by Dave Leroy

Thanks Arash. It was not that I lost the MA values for the 50D; it is that something changed. The original values were still stored in the camera but were no longer accurate. I had to redo the MA's for whichever lenses I had at the time. I remember cluing in to the issue at the time because of comments on DP Review. It sounds like you have done camera firmware updates with no change in focus accuracy.

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I haven't seen focus accuracy affected by firmware upgrade on any of the camera bodies I have had so far.