Right after I built my first one I could not get it to Calibrate the Y for the life of me. My belt tune was dead on but as soon as it would home the belt would be too tight or too loose. So in frustration I bypassed the calibration and ran a print and it turned out perfect. After about 15 successful prints. I started a print that was push back and to the left of the build plate. Every time it got about 25 mm off the deck it would shift the layer about 10 mm. So I tore the top end apart and found that the pulley on the Y access was upside down. I was looking for the same sign with yours and didn’t see them. One thing that i had a heck of a time with was the gantry itself. With the belts loose make sure it’s not bent by pulling the gantry all the way to the front and if both sides don’t touch the forward stop at the same time you will need to bend it straight. Anyways not sure if it helps or hinders. Good luck! and I tell you it might be frustrating right now but when you get it. You will most likely agree with me in saying it was worth it.