The bottom one or two layers bulge outward, so the base is wider than the rest.
flared bottombulging first layerspart wider at the base
Ordered by how often each is actually responsible, not by how interesting it is. Work down the list.
Raise the Z-offset slightly. Do this rather than reaching for elephant-foot compensation — compensation hides the symptom and leaves the bad first layer in place.
Drop the bed 5–10 °C after the first layer. The weight of the part squashes anything still above its transition temperature.