Don't know anything about that hitch, but when a bolt is in a slot, and is supposed to move back/forth, would defeat that purpose if tightened so it would not move. Now, if it is an adjustment bolt for positioning, then it should be tight when in proper position.
This is completely a guess on my part.
2016 Tiffin 40 QBH
2015 38RSSA, traded
2005 TK3 #1869, 10 yrs of memories,
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired