Posted this in the RepRap group as well so I can try and reach the most people for help.
I have a ramps 1.4 board in my custom A8 with a capacitive sensor, everything has been working fine over the last few months, but recently everytime I level my bed the z distance seems to change. I'd go from being at -1.90~ to up to -2.5 and randomly in between. Not sure if my sensor (or capacitive sensors in general being considered inconsistent) has gone bad. but it's really frustrating. If anything i'll probably end up getting a BL touch or something else for auto level solutions if it comes down to it.
That is why I ditched it for BLTouch. Capacitive sensors like that are industrial systems meant to tell a machine when a relatively slow movement has reached it's end. They really aren't meant for precise repeatable readings. Slight changes on the input voltage like bed heater PWM can through them off.
So you solved your own problem! Get a BLTouch!!
I have moved to them myself, you can see it through my progression of mounts.
First I designed my own with a side mount: https://www.thingiverse.com/thing:2734717
Then center mount: https://www.thingiverse.com/thing:2766701
Then BLTouch once I learned my lesson: https://www.thingiverse.com/thing:3160905
That's my latest, also in single: https://www.thingiverse.com/thing:2873811
So yeah, switch it up and enjoy the stability!
Has your mount for the sensor worked itself a little bit loose? 0.6 mm movement would be hard to see...
I have had a very cheap capacitive sensor on my A8 for some time now and it still works well. I have to admit though, that I really like the BL Touch on my Ender 3.
Sadly, no it's rock solid in the holder, and I think it would be weird if it was constantly changing (up and down randomly) would be because of that.