Thanks. Just to make sure. Are you saying that I should disassemble and flip the screw circled in this picture? Won’t that make the screws poke out and hit the motors? Or do you mean flipping the whole part (marked A)?
No, I am talking about the screws holding the delrin nut.
If you have these four on the bottom you can tighten/loosen them slightly while it’s at the top of its travel to see if that’s what’s causing your friction.
I’m trying to understand, but I’m not sure I get it. Sorry, I’m just a total newbie. Any chance you could point out the step I need to do different in the assembly guide? Or if you have a picture of your assembled machine, showing how to reach those screws. Thanks so much.
I’m away from my machine, will try and do you a better explanation when I get back later 
Maybe I can do a quick explanation though.
It isn’t that you have to do anything different, it’s more that this is another set of screws that hold part of the Z raising and lowering mechanism.
The fact that having your Z motor screws loose meant you could raise and lower freely suggests there is some binding.
These screws (for the delrin nut) can also be loosened (but you probably only want to do it a bit) and then you should be able to tighten all the sets bit by bit / wiggle things / adjust it all to get to a point where they are all tight enough but also Z travel moves freely.
Does that make more sense?
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