Pressed in drive nut pulls out on Z-axis

I am building a Prusa i3
The Z-axis threaded rods are threaded through a nut which is pressed into each Z-axis carriage. This press fit is not tight enough to prevent the nuts from pulling out of the carriages when lowering the X-axis assembly. What is the best fix for this? A bit of glue? I don't want to get glue on the threads.

Sounds like your z axis is not running freely on the smooth rods/bearings.

My I3 z axis ends just sit on the M5 nuts,not a press fit, the weight of the carriage should be enough to keep it sitting on the nuts.

I think that was the case. A few adjustments and it seems OK now.