Because this is a cheap mower the entire cross member is way too small
Thus the bush part 9 wears rapidly even if it gets lubricated regularly, which only good techs do ( and there are not many of us )
Then the stabilizer bolts , part 10 both limit the up & down movement and the for & aft movement
If one gets loose or falls out then that will allow too much movement fore & aft
One of the local makers used almost the identical system on their LT's