Error Code: 07,010.43:1944

You are doing nothing wrong.
That code means your print head is not moving into position properly, AKA to slow in pivoting back and forward.
Here are the problems in order of likelyhood.
1. The print head pivot block. When, from the front, you take the left side cover off, about half way back on the lower part of the frame there is a stainless steel block, about 1 inch by one inch square. Most of the time what happens is some ink has seeped into that block and the pivoting of the print head is very slow. What you want to do is remove the spring assembly over that block. It just pulls back and you latch it up and to the left. Remove that block and soak it in very hot water. That softens the contaminating ink for easier removal. Clean the block thoroughly and as best you can pick out the remaining ink surrounding it in the frame of the machine. Lightly lubricate the block with a silicon of very highly refidned oil. I stress lightly.
2. The cleaning blade has stuck to the print head. That normally is caused by not powering down the printer properly or a power failure shutting it down. For that, you have to remove the right and left side covers, and the ink loader,( where you put the ink sticks). That is just held in with pressure tabs. Remove the ink loader then look between the drum and print head, if the wiper is stuck there, gently pry it loose from the print head, and run 2 or 3 cleaning cycles.
3. While you would have the ink loader out, if the wiper isnt stuck, make sure one of the cables to the print head are not holding it back.
One of those 3 will resolve the problem. It is caused by the print head not being able to move freely.

I work at a community college, and appears that at least 4 of the phaser 8400s are having trouble with their print heads. Thank you for giving a something to try to fix this problem.