First, that not a steering box, that's a steering controller.
I don't know how replacing that part stopped it from "popping out"?
Unless you were having an issue with #50, which I think keep the shaft engaged.
There are no O-rings in it.
And you should have replaced the seal when you replace the shaft.
If you did replace the seal then you will need to pull the steering controller and have it rebuild.
DO NOT take the controller apart unless you have a rebuild manual in front of you as each and every plate has to be in exactly the right position, rotation and direction for it to work right and there are a lot of plates!