If you get into the weeds, there is not an accurate method of triggering any form of mechanical stop that involves touch or a hall effect probe. You must get into optics for real accuracy, but that is nonsense for the materials and scope of printing. You would need to eliminate many other variables like the filament accuracy and how backlash and step accuracy are eliminated as issues. As a former owner of an auto body shop with employees, most people do not know what clean is or how tooth is required. Like isopropyl alcohol has its place but is ultimately extremely weak at real cleaning problems. In automotive paint, silicone is a major problem. It primarily comes from tire dressing that makes them look slick black. The amount of effort it takes to remove that junk for automotive quality work is insane. Most chemicals just lush the junk around but leaves or dilutes the issue often making it worse. One of the big tricks in automotive stuff is (to use a a chemical cleaning step first but -) a few drops of dish soap in the wet sanding bucket. The light soap will keep the sand paper clean and working longer, but also makes most work also cleaning work. Anyways, dish soap can be very effective. Acetone occasionally on a surface is also effective. Virgin lacquer thinner is the strongest common solvent but it can react with lots of stuff and you are unlikely to find true virgin solvent. The recycled stuff has a paint stripper component in it that will cause epic nightmares and reacts with almost all plastics. Acetone is much cleaner and consistent unless it is sold for junk like nail polish. The general rule of thumb is to assume a mechanical tooth adhesion is the primary form of bonding unless there is a catalyst involved (2k/urethane primers/clear). That rule can easily apply to 3d printing and bed adhesion. I see a lot of the same types of effects from different surfaces and filaments. There are even special adhesion promoters like Bulldog for spraying plastic automotive parts. I had other tricks too like a mist coating of clear coat. The main trick is to know what grit or “tooth” each thing you’re spraying wants to grab onto and prep accordingly. So I use the general safe bet of sanding my smooth build plates to 600 grit. With sanding, do not start dirty, like you’re trying to embed junk into the surface. Start clean, then knock off the shine to a smooth and consistent matte finish on the entire surface. When it comes to sanding like this, edges and any anomalies are absolutely forbidden. Never touch your edges until last when everything else is done. Edges are always thinnest and most vulnerable to causing issues especially for the inexperienced. Clean it with acetone like once or twice a year and then sand it to matte, clean that with dish soap, then alcohol with each print. That will completely eliminate contamination as a cause. Perfect first layers are possible with enough fussing with the software. If you really want to level the bed with hardware, use a dial gauge clamped to the extruder. That will remove all of the averaging and inaccuracies from probing. You would need to get into optics for true accuracy like with closed loop control systems that are an order of magnitude more expensive than 3d printers. These are precision machines with no accuracy. The 0,0 home location is always slightly different, but all measurements are based upon this location. This issue becomes relevant with IDEX and CNC. Going we beyond these, in optics accuracy requires a defraction grading and alignment of light patterns. I so want to get into that one to grind my own telescope mirrors. If you have v-roller wheels on extrusions, one other major potential issue is that extrusions have a relatively large twist tolerance component in their specification. It is extremely difficult to detect this kind of twist, but it is a major potential issue.