Hi,
one simple thing to test for loose spindle is:
-chouse slow jog speed
-hold the spindle with one hand
-jog with the other had backward and foreward and try to block the spindle
there you can feel if there is any loose part.
an other test is to do G1 moves in the MDI, allways the same distance forward
and backward, mark your startpoint and endpoint and check that it goes allways to the same
points.
Thomas