Yeah or the bed itself is fine, but it's on a bad bed support. That's why even a perfectly flat glass bed plate can be completely uneven since the structure its

Yeah or the bed itself is fine, but it's on a bad bed support. That's why even a perfectly flat glass bed plate can be completely uneven since the structure itself is crooked! Considering that quite a few printers are self assembled too (with basically no torque specs, and users that have little means to build it accurately), it's just compounded even more.