My x-carriage does not fit.

I had many other projects going on and then took a long vacation. But now I want to give you an update on my new build.
As I posted before, this one was nearly completed made with CNC aluminium parts.
But hen I put all together the x-carriage just did not move to the mechanical end stop.
At that point I decided to spent my time on other projects and revisit this build later.

The problem is the CNC made x-carriage.

Today I finally inspected what the issues is and found that the belt was bending, when I moved the x-carriage with force to one of the ends.

In this picture you can already see the problem, but on the first look it was not that obvious to me.

In case you don't see it either, the problem is that the milling for the belt is not deep enough.
On the left side you see how deep the milling is, and on the right sight I have shown how deep it should be. The blue rectangle represents the belt.

So why is that? Well the belt runs in the middle of the two rods as you can see from the x-ends below. And so it should on the x-carriage as well. But they milled the cavity not deep enough. They only milled it to the middle of the rods. That is why the belt is pushed to the side by approximately 2.5-3mm.
Which is not a problem as long as you don't push the x-carriage all to the end of one side. But as you do usually, at least for the homing, it is a problem.

I do have a CNC mill on my own, so I could mill the part myself to make it fit. But then bits with the right diameter don't have enough length to cut the required depth.
In parallel I will contact the seller and see what he has to say. I will keep you updated.