leadscrew has end play, the thread length drifts

I can push the leadscrew along its axis and watch it move. Maybe fifteen thou. Threads I cut are a little longer than the dial says they should be, or I'm bad at counting. Both can be true. Is the end play the first thing, or am I shopping for a problem.

Fifteen thou of end play shows up in the thread. Adjust the end bearings until the screw turns free and the push is a couple thou, not fifteen. Count after that. Don't buy a new screw to fix a nut you haven't set.

Took the play down until a push is barely a wiggle. A 1 inch thread is an inch now, near enough that the nut doesn't argue. Counting was also a little optimistic. Both were true. Annoying.