The problem is that nothing holds these threads in there. They sit in a slot for them and the roller's screw holds them in. So I install those screws even when I don't use the rollers.
You need to use a pick and pull those threads (slide nut) back towards the hole.
Maybe tapping on it while it's upright might do it? It slides very easily so don't shove the screw in there.
Oops, Jeff S also posted now.