Machine had been solid for quite some time. I'm now getting what appears to be a drifting Z height as the job progresses. I'm using a dial indicator to show what's happening. After it does its rapid, you can see it go to -0.01117 accurately. Then, as the job progress to a couple of different Z heights, every time it returns to -0.01117, it's inaccurate on the dial indicator. (first issue observable at 0:22 in the video)
Here's the video of what's happening:
https://youtu.be/KynRv2ybuO4
If I stop the job and issue an MDI to Z0.0, it returns accurately to 0 on the dial indicator. If I use the MDI to control the Z height manually and make it step to that -0.01117, then step to other increments and return, it works fine. I've also done a simple square routing, stepping the Z height down without issue. The Z motor is also calibrated accurately.
That makes me believe it's something to do with the project file (though I've been using it successfully without changes) or the controller itself. (Leadshine mx4660)