It's interesting to see his progress in making a commercial quality machine, with what appears to be skills he has from previous experience, and no drawings. I like that a lot.
I'm curious to see how his repurposed CV axle joint works under high torque and articulated angle of the machine. I think he kept the center of rotation of the joint with the pivot of the machine.

I say that, as I've seen other youtube vid's of making AWD autos with repurposed transaxles, differentials and require large swing movements relative to the center of rotation. Fiat has long travel versions that I saw in one video. But to me, that's for a 4 bar link that has wrong geometry. But I know nuuuting.

My neighbor has a biz that services motorcycles and ATVs. He has customers that put in lift kits on the front and rear (it's crazy that these toys can cost >$40KUSD), which forces the CV axle to operate at a continuous angle, and from me seeing, it's 25-30 degrees, they overheat. He showed me one that within 40 minutes of driving from new (a 4 door with AC and winter heat), got red hot and split the outer housing. But that's at road speeds. l do see with front wheel drive autos, they are typically zero angle.

I know, it will not be the problem with this machine as subject video, as it's walking speeds. If the center of pivots do not match, I could see that wrapping the joint around the drive shaft.