The bed was never level along the Y axis from day one. At first I thought it was an issue with the 4 corner clips and was waiting to implement Tesseract's(Jeff) mod to fix it. As the issue was bad enough to prevent me from printing even small object often, I asked for Jeff's help. We had a skype video call and tried different things. Boro glass turned upside-down, rotated 90 degrees. No change. Boro+heating element removed. No change. We came to the conclusion that it has possibly to do with the Y rails. On the first video, using the dial(in millimeters-one full turn=1mm) I start from Y200(extruder all the way to the back). The bed first gradyally drops about 0.25mm and about 50mm before the Y-home positions it rapidly jumps up by about 0.5mm! Again this big jump happens during the last 5cm(50mm). To show that it hasn't to do with the boro, ther is a second video where I have laid a laser pointer on the bed(along Y-axis) ponting to the wall, and you can see the dot moving on the wall. So it is not a curve on the bed, rather than the whole bed rotating as it slides along the rails.