And before someone tells you to check your belt tension…and most people are way wrong on this actually but they don’t listen. Your X axis belt is a toothed timing belt. They are not supposed to be tight…just taught enough so the belt doesn’t jump a tooth. But read this sentence or two on belt tension from the actual manufacturer of timing belts.
Timing belt installation should be a snug fit, neither too tight nor too loose. The positive grip of the belt eliminates the need for high initial tension. Consequently, a belt, when installed with a snug fit (that is, not too taut) assures longer life, less bearing wear and quieter operation. Preloading (often the cause of premature failure) is not necessary.
O.k….so there you go. I know this anyway as I was a field engineer for a few years on high end robotics and we had to be taught proper timing belt tensions. People, including myself, tended to set them too tight. So I doubt any belt is too loose…actually I can almost guarantee it. It’s a red herring around here it seems unless it is so slack it jumps and that is so loose you would easily see it….easily.