Slop in the motion system reads as wavy walls or apparent layer shifts. This is mechanical, and no amount of profile tuning hides it.
Phase 0 — Mechanicalabout 15 min
How to do it
Find the eccentric nuts on the X carriage, Y bed, and Z gantry.
Turn each in small increments until the wheel just grips and will not spin freely.
Move the axis fully end to end. Any tight spot means the rail is not parallel — back off and re-check.
On linear-rail machines, check for rocking at the carriage instead.
How to read the result
Each wheel turns with light finger drag and cannot be spun freely, but the axis still moves smoothly end to end by hand.
Does your printer have this?
Look at how the print head and the bed are carried. You HAVE V-wheels if you can see black plastic wheels running in an aluminium extrusion channel, with a six-sided ECCENTRIC nut behind one or two of them. You have LINEAR RAILS instead if the carriage rides on a steel rail with a metal block, which has no preload adjustment at all — you check those for play and replace them if worn, you do not tune them. Either way there is something to check here, so this step rarely does not apply; what changes is whether you can adjust anything.