I have an Anet A8 and I currently try to improve the y-axis (with a tensioner and a frame to support the structure). Now after I dis- and reassembled the y-axis, I get a loud rattling noise when homing the y-axis (and also when moving it stepwise from within the firmware). After the rattling goes on for a second or two, the printer halts and asks to reset. During the rattling, the print bed moves much slower. It appears to only rattle at the end of the axis, close to the endstop, however the point at which it starts to rattle appears random.

I tried a tighter and looser belt and aligning the frame. When moving the bed manually, it does require some force, but it does not appear to be tighter at the back side of the axis. Also nothing seems to block the path of movement.

I noticed that with a tighter belt the rattling starts only closer to the end stop, however it appears like I have to overtighten it to work properly. I got it to hit the end stop this way without halting, however it still produced the rattling sound. Also the y-stepper motor made a high pitched humming noise after this operation.

What else could I check or do about it?

This is a video showing the print bed with the rattling sound:
<https://www.youtube.com/watch?v=H0Xhz2GtUYQ>

View from below:
<https://youtu.be/oTEuZUWD0ZM>

This is the motor mount:
[![enter image description here](https://i.stack.imgur.com/7xmJM.jpg)](https://i.stack.imgur.com/7xmJM.jpg)

And this is the tensioner with the support frame:
[![enter image description here](https://i.stack.imgur.com/5wz8u.jpg)](https://i.stack.imgur.com/5wz8u.jpg)