Swinger Tight Window Issue

Is there anything in the vent window channel?
Nope, but did a double check tonight
Is the channel pinched?
Nope, nice and straight
Did the glass and the vent frame come out of the same car and worked properly before?
I replaced the vent frame but the glass was from my car, and I was told when I bought it that it was in good working order
So heres an update tonight. I thought something must be wrong, so I removed the entire assembly and laid it out. After pulling the glass out of the channel (was VERY difficult) and examining it, I noticed that the bottom plastic strip on the glass had come loose. So after making sure the strip was good and secure in the hole, I sprayed some WD40 Specialist white lithium grease into the vent channel and reinserted the glass. It was an immediate improvement, and after a few times of moving the glass up and down, it was moving as everyone has been saying, tight, but not so tight that it cant be moved by hand. So I reinstalled the assembly and regulator, and the regulator moves the glass as it should. Now I just need to adjust the alignment, thats another nights project. Then I will tackle the other door, and Im sure it will go MUCH easier than this one, the second one always does right?
Thanks to everyone for all their advice, it was very helpful. And if I can add my own advice to someone doing this, run a cleaning tap through any threaded holes, and a die over any bolts/studs, it sucks when your fasteners are dirty or rusty and dont go back in properly.