My IDEX build has been working reasonably well but I have recently had a string of failures when attempting long prints. In each case, the failures occurred after several hours and always because of sticking and lost steps on the Y-axis. Sliding the extruders along the X-axis was nice and smooth, but moving the whole carriage in the Y direction was noticeably more jerky and sticky. I suspected that this was likely to be the cause of the print failures. I removed the top cover and inspected the movement more closely. The cause was then quite obvious - I had failed to keep the Y-axis drive pulley is away from the side wall and the friction of rapid to and fro movement had started wearing a hole in it. Sliding the pulley a couple of millimetres to the left has completely resolved the stickiness and binding and hopefully put an end to the failed prints.
I had a, luckily, worse case of this very early on, with the Y axis completely bound. Took a while, but ultimately found the same thing, having this pulley touching the edge. There's not really a whole lot of space in there, and one millimeter is about all you need from the edge, maybe less, before you end up pushing the other side into that wall. I recently had a similar thing, though a different cause. X was smooth, Y was squeaky. I went for the same spot initially, but that was fine and still in position. Eventually I discovered that I'd pushed a little too hard down on the Y motor while tightening the screws that hold it in place. I've had that on and off a few times, printed Alex's mod for an extra mm of gap, printed the cork piece in flexible material, and washers for the other side of the wall, all in an attempt to try to silence the Y monster; all unsuccessful. But that meant I'd become a bit too familiar with having that section on and off and had overstretched. Once a released the tension there, the sound went and everything was back in working (semi) silence.
