Homing issue, Axis not resetting to 0.0000

Good day everyone. I’ve recently noticed a problem pop up that I’ve been able to resolve, but can’t figure out what the cause of the issue is, and it is annoying me to no end. When I ‘Home All’, X,Y and Z all move to the correct position but instead of registering 0.0000" in all three axis, a v very small number gets registered. This has varied, but this is what I witnessed today, for example ( X=0.0015, Y=.0005, Z=.0008"). At the very movement the Axis normally back off the sensors and register zero, there is a slight “thunk” noise whenever this happens. Closing Mach4 and rebooting always clears this up and homing zero’s out correctly immediate after rerunning the program. But, damn if it doesn’t creep back in again.

At first I thought I might well have forced the motors to miss a few steps. I’ve been doing some re-calibrations where I have opted to home much more frequently so that may be the cause of my noticing the issue. But interestingly, when I HOME the machine and this problem pops up, I move all 3 Axis into positive space and re-HOME (off the sensors). When I do this the problem doesn’t resolve itself and often registers different numbers than previous HOME routine. They are
always small, however, and never more than .0015".
I’ve check for mechanical interference and the belts are pulleys are all low hours.

Thank you all in advance for your feedback.

Are you by chance using position feedback? Servos or steppers?

After this happens, if you click the History button in the bottom left corner, do you see any relevant status messages?

NEMA34’s, purebred AVID system. No history of mention.