I remember the knobs under the heated bed are quite tight; they’re usually only used when you need to perform bed leveling. But the bed is usually leveled one time at the factory before shipping.But I don’t think this is what’s causing your issue.
Still, I’ll add the steps just in case.
After the bed is mechanically leveled, you normally only need the software-level compensation from now on (see image) and won’t touch the mechanical knobs again.
before mechanically leveled start ，you can printing the adjust tool：U1 加热平台螺母套 - 免费 3D 打印模型 - MakerWorld
than fllow step in machine：
Tips:
- When deviation is large, adjust in 1/4-turn units.
- When close to target, switch to 1-3 mm units per nut rotation.