I have looked at video1 over and over and over and over again.
Here is what I have noticed. It appears that the sound that is not “smooth” only occurs when the router is moved up or down on the Z axis and that sound seems normal to me. Can you set up a file to move the X axis without moving the Z and see if you still get the noise?
Also, I don’t know if it’s because I am viewing the video over the internet or not, but it seems that your X axis V wheels are not rolling all of the time. I see some spots where it doesn’t roll, or the video is dropping frames. I tried to download the video to play in from my disk, but I wasn’t able to do that.
The sound that it makes when you are moving the Y axis by hand is normal. When you move the X axis by hand I do hear something that is a little off.
Do you know how to dump out the grbl parameters (using the $$ command)?