LCD displays the question marks
This configuration: Repetier-Firmware V1.02 Mega 2560 + RAMPS1.4 + LCD12864 + SD. The coordinates x, y, z change every second to the question marks (?). What is wrong?
You did not home. Until you homed this indicates that real position is unknown and should not be trusted.
I see this too. But I homed the Z... lcd shows 0, but then when steppers are deactivated the ??? returns changeing from ??? to 0.00 this is normal?
you have to home ALL Axis, not only Z
When you disable motors position can change, so again position is untrusted.