Gantry hits physical barrier before hitting Y-endstop

Just like title says, the gantry is hitting the z-guide before it hits the Y-endstop. This causes the gantry to continuously crash into itself during Y-homing instead of gracefully stopping once it hits the end.

I received a response from the team which said that the eccentric guide should hit the endstop, but it doesn't hit it because the gantry's top guide hits the edge before the bottom eccentric guide is able to hit the endstop. Here's a picture to illustrate:

Would anyone know why this is happening? Is this a fault during my construction or a fault with the dimensions of parts?

For the worst case scenario, I can append extra material to the eccentric guide so the gantry can hit the endstop faster, but I'm hoping there's a native solution to this problem.

Thanks!