If I home my Zed axis, it touches the switch, reverses course a touch, moves up slowly to re-engage homing switch, and backs off so the switch is barely off. PERFECT!

When I try this on my X axis, after touching the switch it backs off several inches, slowly walks back to the switch, touches it and moves off several inches to "home".

 Why the several inches distance?

Check what is in the Home Off. column under Homing/Limits
 

0.0000 in all axis fields

Sticky/Slow switch?

No. I think it's something in the settings that I don't have right. It's a new machine that I just built.

'it's anew machine'
Sound like hardware to me too.

Cheers
Roger