ABL doesn't automatically measure the right distance to your bed. It has no idea where your nozzle is. Your nozzle is somewhere between the sensor and the bed, but the sensor doesn't know. You have to calibrate that. If your nozzle changes (swapped, comes loose) or your bed changes (moved, replaced, damaged) then you recalibrate.
There should be an option to micro step your Z. I have a Sovol SV06+. I run the ABL routine, then print a 1 layer square. If that's too close or too far, I adjust. My options are 0.05mm and 0.01mm steps. Adjust, reprint. Adjust reprint. See the images here, for what it should look like. https://help.prusa3d.com/article/first-layer-calibration-i3_112364
I'm agree! But look at my picture, how can it be good at some point, and to close at others?
When my Ender 3 S1 (not plus) had bed leveling issues, the problem was caused by backlash on the Z axis. It's important that the Z axis be just loose enough that downward motion is driven by gravity. If instead the Z screws have to "pull down" on the gantry, then the height will be too sloppy for ABL to make fine adjustments.
It doesn't help that, by the power of marketing, people can mean multiple distinctly different things when they say "bed leveling".
What you're referring to is Z offset. This is the difference between where the endstop or probe triggers versus the actual Z coordinate of the nozzle. This is generally what you're trying to set with the paper test. The paper test is only mostly accurate, though. A set of feeler gauges will do the same job with better accuracy.
It can also mean tramming, which is making the bed itself planar to the printer's gantry. This is what you're doing when you adjust the 'bed leveling' screws on a printer or what happens automatically if you have triple lead 'bed leveling.' It pretty critical that Z offset is set correctly for autotramming. Manual tramming is essentially setting Z offset to be consistent at each of the bed adjustment points.
Finally, mesh compensation also gets called bed leveling. Even if you have a perfectly trammed bed, the reality is that real, physical things (like beds) are never perfectly flat. Mesh compenstation probes multiple points along the bed, registers the difference between Z0 and the probed point, and builds a mesh that the printer uses to compensate for variations in the bed surface. The denser the mesh, the better the printer can compensate for small variations in surface flatness.
All of these things are complementary and will have an impact on each other. The fact that they all get lumped into "bed leveling" causes a lot of confusion for folks when understanding what each is and does is pretty important to get the most out of a printer.
This can be caused by gantry misalignment/warping, or not registering the bed mesh properly. Also, maybe the bed is warped in some way that was in the middle of the test points, so maybe a finer mesh could fix this.
That looks like just AB and no L
Given that this doesn't look uniform, it looks 'random' -- you need to check that your hot end is actually secure against the X carriage.
If this were uniform, like it faded out from a low spot - I'd tell you there was debris under the bed, or a mis-measure on the probe (it happens, they aren't perfect)
ABL isn't a solution for leveling problems. ABL is a 'lazy' test for an already-well-tuned printer. If you're having leveling issues, an ABL won't work right because it assumes everything is working perfectly to begin with.
