The skew problem happens when loading the paper, not when you hit a "print" button. The machine rejects the load, shows a red blinking light that instructs you to hit the "down arrow", and backs up the paper so it's not in the feed section any more. Either the rear feed or the sheet feeder will reject the paper feed if it's in there crooked. You'll have to pull it out backwards and start over.
In addition to the clothespin technique that constrains the left guide on the rear feed, here's how I feed large paper through the sheet feeder if I prefer to do that (which I do most of the time):
1. Place the paper into the sheet feeder down behind the curved guides, and set the left guide so it's just against the edge of the paper, with the bottom of the paper back against the rear wall of the guide, and the edge down to the back bottom of the guide area. Don't let the bottom of the paper curve towards the front of the machine. Make sure the guide isn't pushing the paper into a sideways curve, but is just against it to hold it straight against the right side.
2. Reach your fingers down behind the curved guides, and use the backs of your fingernails to get the paper straight across the back (and all the way down to the flat bottom, as above).
3. With everything straight and steady, take your right hand out and hit the rectangular "down arrow" button. Reach back in, and keep the paper straight and down with just a little downward pressure. Keep your fingers no closer than about an inch to the bottom of the paper. The machine will think for a bit, then it will make a whirring sound. As soon as that sound stops, it will make a grab for the paper with a "snap." You will automatically take your fingers out of the feed area when it does so. Trust me on that. You will. The machine will pull the paper into the printer to the start print position and stop with the usual "up and down" motion that verifies that the paper is straight. It will indicate "ready" and you'll have a green light if everything is fine. With this method, it works fine for me every time. Now, the paper is loaded, and it's not going anywhere.
4. Go back to the computer, make whatever checks or adjustments need to be made to the printer driver on the screen, and then hit "print." The printer may make some more noise as it cleans the head, or whatever it does first, and then it will start printing when it's "dang good and ready."