Issue With New 3D Printer (Reprap Prusa i3)

[printbus]

I don't see the Z-axis doing much of anything in the video. Are the motors being driven with the usual reprap driver with a voltage adjustment? If so, have the stepper motor drivers been adjusted to ensure the motors are being driven properly? Do you think the Z-motors are trying to drive in the right direction?

That type of shaft coupler is notorious for not gripping the threaded rod very well. The issue is the threaded rods are technically undersized a bit compared to a smooth shaft. There's a similar shaft coupler that uses set screws to grab the shafts that does better, but many of us improve the grip with the kind you have by adding some foil or metal tape onto the threaded rods.

There's a problem in the Y-axis too, leading to what sounds like the Y-motor either skipping steps or if belt driven, the gear on the Y-motor skipping teeth on the belt. That could be a number of things wrong in the setup, from home/zero position and bed size definition in the firmware to wrong endstop switch position or setup, or incorrect motor direction, or...?