Also check that the bed itself is still flat.

Remember that despite all the software and electronics printers use, they are ultimately hardware, and hardware wears out and breaks sometimes.

My glass bed has warped over time with heat cycles to the point where the center of the bed is a full mm lower than the edges and corners. Every slicer setting in the world can’t fix that. The fix was a new bed, or you could work around it if you have a touch sensor to make a bed mesh, but then the bottom of your parts still won’t be flat.