Auto-Select all doesn't work in position window

I often manually set positions (and other values). So, I need to clear out the existing values (which are often very long) and enter my own. 

What I do is this: I click on a keyframe, then on "Position". I get the small "Move Tool" window. I click into the X value area, and the entire value is selected. Perfect; I press 3.14 (or whatever) and done. Now I click into the Z value area, and ... Nope. Nothing selected. I need to clear out the value by hand. which is problematic since the left/right keys don't work; they move the scene view (which also wasn't the case for the X field).

Note!!!!!! If I first click in Z, everything gets selected, but then X doesn't work. Seems to only affect the second and later field I click in. Strange.