Z plate sticking in one region

Just putting the finishing touches on my new SO3 XXL and hoping to try out a first run tonight. However, I noticed one potential problem with the Z plate on my machine: Moving it manually, the plate slides well without slop for most of the range, but when it is about 1cm from the top, it seems to get stuck. Moving it back and forth, it always wants to stick in that one spot. A decent amount of push is required to move it past this region, and I’m worried that this may be a problem during operation.

Before I try out the electronics and a test run, I am hoping someone can give some advice on how to correct this. This didn’t seem to be a problem when I first put the XZ carriage together, and even after putting the springs on, it seemed to slide all the way to the stop rails without a problem. The only change I made afterwards was tightening one of the eccentric nuts on the X plate wheels because there as a lot of slop in it. That seems to be corrected, but now I have the Z problem. I feel they are not correlated, but I may be wrong.

Please try removing one of the springs — suspect that they’re the cause. The belts should be taut enough, and the motor powerful enough so that it’s not an issue in practice, but it’s good to check.

If that’s not it, please check that the V-rails are installed parallel to each other, and that the carriage V-wheels are adjusted so that it is plumb. Inspect the belt (easiest to use a small dental mirror) that the teeth are in good shape, and check the Z-axis motor pulley set screws: http://docs.carbide3d.com/shapeoko-faq/shapeoko-3-how-to-check-the-pulley-set-screws/