Problems at K8400 calibration

Hi.
I have successfully assembled the Vertex 3D printer the first time. The X and Y axis were a little decalibrated(around 2 steps each) so I decided to reassemble it in case I made any mistake. After reassembling it and carefully following the instructions I ended up having a perfectly calibrated X axis but a totally screwed Y axis.
When I manually move the printhead to 0,0 it successfully goes to autohome position.
I have also attached 2 video files where it can be clearly seen that the printer can do the autohome function but when it reaches that position the Y axis goes wild.
What did I do wrong and what steps should I take in order to correct this?
https://photos.app.goo.gl/kEDsIdNypzxgQo4X2
https://photos.app.goo.gl/5dRYzFJBY5S2lIAr2

Thank you!

You should look in this link.
http://www.k8xxx-3dprinters.crimed.be/w/index.php/XY-Carriage_Alignment