Haas VF-3 home height changing

Hello all, I’ve been a lurker for some time now, lots of great information here. I purchased a 97 Haas VF-3 last September and have been running it on nights and weekends gaining experience, and customers along the way. I’ve tried to be pretty consistent during startup, I’ve made a program to warm the spindle and cycle the table a few times before I get started working. I also touch my tools off on a 2-4-6 block off the table, as well as a haimer probe for a z reference. I have began to notice that the reference height (when touching off with the probe) would float some every startup, and I started to write it down every startup and verify at least one tool before running programs, no problems it was manageable. This last Saturday it was off by 5 thou, and by writing down the numbers it had slowly drifted one direction (can’t remember if it was up or down) I went to do a tool change and the tool change height was different enough for it to not change tools “well”, it worked but it sounded rough. Is there a limit switch I can check for looseness? Or maybe a loose coupling between the servo and the ballscrew? Any help is appreciated, I would really love for the z height to repeat more consistenly. Also i’ve had the entire motor and transmission off, I may have unintentionally damaged or loosened something then. Thanks.