One takes off and then the other catches up.
Given that the second stepper is loose, the most likely problem is that the second motor is not being energized at all. The second one “catches up” because it is being dragged along with the first motor. The following can cause that problem:
- Issue with the wiring
- Bad stepper driver
- Stepper driver having the current set too low
- Wrong firmware
Theoretically the problem could be a bad stepper motor, but that is exceedingly unlikely.
You can troubleshoot to identify which one is the problem.
Swap the stepper wiring at the control board between X1/X2 Y1/Y2. If the problem remains with the second stepper motor, then you have a wiring issue.
Send an M115 to your control board from RepetierHost and look at the response. This should tell you what firmware you are using. You are looking for “Dual” in the version.
If you are using DRV8825 or A4988 drivers, then you must check the current. There are a number of tutorials on the internet on how to set the current for these drivers. It is a matter of setting the correct v-v-ref voltage. The v-ref calculation is different between the two drivers.
Assuming all the above check out, then you can check for a bad driver by switching the drivers between X1/X2 and Y1/Y2.
Note that unplugging a stepper while it is energized will often toast a stepper driver.
As for your screen, if you are running a smart controller like this one, don’t assume any diagram is correct and try all combinations of both plugs and rotations of the two cables. You may have to trim the “key” on the cable to rotate the connection. Also make sure you check the various brightness settings using the potentiometer in the lower left of the display at each cable configuration.
If you are running a TFT35 display, be aware that there are three separate cables that must be connected.
Posting a picture of your control board might help us spot issues.