Issues assembling Lead 1515

I have put this beam for the y axis on this gantry plate two times. The first time I realized I used the wrong tee nuts. I used the drop in accidentally so I took it apart and used the correct tee nuts. The tee nuts have a flat side and a side with a circle extrusion with what looks like teeth on them. When I threaded the nuts onto the bolts, I did it with the extrusion facing the gantry plate. The beam went on, squared, and tightened down fine. While rewatching the video at about 13 minutes, it looks like he puts the tee nuts on with the extrusion facing away from the gantry plate so they would slide into the slot of the beam facing the center of the beam and not the plate. So so disassembled it once again to put the nuts on the way he shows. Since doing that I have spent about 5 hours trying to get the beam to connect to the plate with sliding it on and it will not work correctly. I also noticed on the gantry plate assembly portion the parts needed list requires some aluminum washers that do not get used in that assembly. In realizing that just a few minutes into the video that mistake has been made, I thought it may be possible there are other mistakes made. Do the tee nuts go on with the extrusion facing toward the plate or toward the inside of the beam track? Would it be okay to put them on facing the plate if it’s supposed to be the other way or what kinds of issues could that pose? I just want to get this together and start using it but, I want to do it correctly so I don’t run into any issues later.