I think the first step is to make sure all the screws are secure and tight, especially the screw on the motor, coupling, and roller. Then I would try to switch the motor cable (such as switching x cable with z motor cable) to see if there are some motor issues. The below is the video to demonstrate how to check the motor. Hope this would help. 

Hello Lee W, I have exactly the same problem of you.

I received one Ender 5 plus yesterday, I printed my first project for 4 hour without any problem but this morning the machine dont work.

I have make the same symptoms as you : 

- at the start X and Z axis works fine, then Y axis make a terrible sound, after this, X axis make also a terrible sound.

- Y axis dont go to is home switch, and when trying to move the Y axis manually it alternates between moving forward and backward regardless of which Y axis button is pressed.

Firware version is also 1.70.2 BL

Have you find a solution to your issue ? 

I make this short video like you...

CYT, regarding your informations in the video, I tried to inverse X motor & Y motor, and the issue is now on the X motor.I don't try to open the control box, because its a new machine and it's a little touchy for me..

@vincent-45 For me it looks like the motor is not working well. Did you fix the problem now? 

Just finished assembling mine and have the same problem, will double check for anything loose and try the motor check. anyone solved their problem?

@ski The problem should have not been solved.
1. Double check the screws and wire connection. 

2. Check the video that CYT shared, do a stepper test between the X-axis and Y-axis or Z-axis. In this way, you may find which part is failed.

3. Mainboard issue.

Might of fixed my problem.

the screw for the lower eccentric guide wheel on the X axis was loose, tightened and so far it has worked. Time will tell. Hope this information can help someone

@ski Glad to see someone fixed!　Thanks for sharing. ?