Okay that is actually a 2015 Troy-bilt Horse XP (in Craftsman dress) mower which is a MTD.
When you changed the fan steering gear did you also replace the spacer bushing for the bolt that goes the center? They do wear out.
Then the center bolt which is a 3/8-16 x 1 fully threaded needs changing out to one that a long enough unthreaded section to go thru the spacer bushing. The reason here that the threads gets smushed and then fan is free to move off center. It doesn't take a whole lot to cause problems. And this hoping the frame hole for this bolt isn't wallowed out.
Spacer/Bushing is PN 750-06192A
Also since things now slipping again make the steering gear didn't get damage. Mtd makes these by press forming the gear which an easily damage gear. I wish Oregon made the 21" steering shaft but they don't as their gear is machined and much more durable.
Now the rest of the steering components need to be lubed good so it moves freely. But don't any oil or grease on the gear teeth of the fan or the shaft gears. Just causes dirt/trash get stuck in there.