Quote Originally Posted by lucidpsykosis View Post
what does it mean when the front, back and sides feel right but the center is tight?
That is normal, the print head sags very slightly in the middle. I usually level the bed perfectly with a postit note, then every so slighty tighten each thumbscrew just a tiny amount. Do all 3 the same. But it will print fine when the print head is a little closer to the build plate.

It helps if you decrease the weight of the print head by removing the unused stepper motor at least when not in use.