Nothing on this printer has cost me more evenings than the first layer. Everything downstream is fine: the slicer is fine, the filament is dry, the temperatures are sensible. And then the nozzle drags a sad little smear of PLA across the glass and I am back to the paper-under-the-nozzle ritual, front-left, front-right, back, centre, round and round until I have convinced myself it is level. It is never level.
The thing that finally helped was accepting that "level" is the wrong word. The bed isn't a plane, it's a gently warped sheet that changes shape as it heats. Chasing the four corners with a manual screw was always going to be a losing fight, because the middle does whatever it likes. Once I framed it as compensation rather than perfection, the whole thing got calmer.
So I gave in and fitted a probe. A cheap BLTouch, a mesh of points, and a G29 before each print. It is not glamorous and it adds a minute to every job, but the smearing stopped and I got my evenings back. If your prints fail on layer one and nowhere else, stop tightening screws and let the firmware do the measuring. The war isn't winnable by hand.