Quick Focus (AE-L/AF-L) Button method Question.

nonicks wrote:

When you are in Manual Focus Mode and use AE/AF-L button to assist, do you hold down the AE-L/AF-L button (after achieving focus lock) while pressing the shutter. OR do you release the AE-L/AF-L button, then press the shutter?

In some situations I found that holding the AE-L/AF-L button while pressing the button yielded more accurate focus.

Also in some occasions, I notice when I release the AE-L/AF-L button then press the shutter, the focus distance shifted when I press the shutter. Anyone experienced the same thing? Is this a known issue?