nanoDLP

Sometimes, when I use the  z-calibration to remove Z axis, the machine will run a wrong range,or other strange way.

like that when  I click

http://192.168.1.103/z-axis/move/down/micron/10000       

to move down 10mm

it will run as  nomal speed for 9.5mm  (probably  9.8mm,  9.9mm anyway no 10mm)
and then ,the Motor will run as a very slow speed, maybe it will cost 8 to 10 seconds to complate.

or sometimes like that :
click
http://192.168.1.103/z-axis/move/up/micron/50000 

to move up 50mm, and Z axis maybe run 30mm or other, and it stoped .

At first, I think is that some problem in marlin firmware ?

so i connect the machine to the PC, use PrintRun to control it.
it's not slow down. Z axis moved normally.

Then I set a customized Buttons  and the Code is :
G1 Z{[[CurrentPosition]]+10} F200;
[[PositionSet {[[CurrentPosition]]+10}]]

to move up 10mm. 
Z axis moved normally too.

It seem like the problem is form the page  z-calibration?

My nanoDLP version is the newest  1827.