The ball bearing stops you from pulling operating handle when in upright position.
Look inside at operating handle,
Along the handle there is a small flat edge which lines up with a square gap
with a sloping edge like a small ramp shape.
Ball bearing goes inside there.
If its in right place, it will stop handle being pulled whilst upright.
When you tilt back, ball will roll out and handle will pull easily.
If ball is a bit rusty it sometimes gets stuck in there.
WD40 & small wire brush or bit of sandpaper fixes it.
Tim.