X-axis drooping  

X-axis drooping

I recently rebuilt my 2.5s after a hotend leak wrote off the hotend.  I used all new 3D printed parts for the X-axis and extruder assembly. Fit was good on these, snug but not impossible.  I did ream the 8mm rod holes with a drill bit to get them to fit. I also used new bearings on the Z rails.

After the rebuild when I power off the printer the X stepper motor side of the axis drops around 2mm.  It remains stable whilst power is applied to the steppers.

I did used to have the Z drive rods lubricated but I read that was a bad idea and so have cleaned off the lubricant now.  Could it be this has worn the captive nut enough that there is no longer enough friction to hold position under the weight of the motor?

I also checked the X axis length, which is 307mm between the orange printed parts.  I believe this to be the correct value reading the comments in the build docs to give the correct spacing.  So I don't feel that it's the axis is too long and pushing it out of alignment.

This was originally a Mk2 from when they first launched so parts are starting to get quite old now so wear seems like a reasonable explanation.

I don't have a photo handy but this show what's happening using the prusa stock photo.

Any help would be appreciated as it's tiresome having to redo the level each time by maxing the Z travel.