Y Axis Grinding and prints flopping  

Y Axis Grinding and prints flopping

Hi guys,
I'm making this post to diagnose an issue that occurs with my prusa I3 MK2, that I bought used in assembled, that has been giving me small problems since I initially purchased it.

The majority of the problems have to do with calibration, the PINDA, XYZ cal, and I've somewhat figured it out, or at least found a way around those issues, and I've actually been able to get some really nice prints very recently.

if you want to know more about those previous problems, which I don't think apply too much in this case, the link is here.
https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f80/lots-of-problems-i3-mk2-firmware-software-related--t19777-s10.html

Otherwise, here's the actual problem I'm trying to solve right now. I'm certain this is having to do with the y belt either being too loose or sticking out or something of the sort. Video link below.
https://photos.app.goo.gl/sn3DVNmie3zg3a436
The initial grinding is happening after I hit the start print button and the printer hears, when the bed wants to make its way all the way to the back to Auto home. After the initial grinding, the mesh bed leveling goes fine. However, while laying down that first line to clean off the nozzle, the printer makes a similar grinding noise (except going in the opposite direction) and the printhead doesn't move all the way to where it should be.

The nozzle tries to print too low because it's in the wrong location and the print is obviously messed up and needs to be aborted.

The reason behind the initial grinding is that during the final steps of the AutoHome, the print bed wants to hit the Y endstop, but something is preventing it. It doesn't look like anything visible, and I've tried using sticky tack on top of the end stop button to get around the problem, but I need a more reliable reason.

The second grinding, however, is what' s really throwing off the prints and I honestly have no idea why it's happening or how to stop it. The sticky tack worked before but it's very inconsistent. Any help would be greatly appreciated. Thanks so much everyone!!!