Forcing a part into "home position"

I have a design with two parts (at the moment):

• a fixed 10cm ring with vertical tracks
• a freely rotating block with a cut that may freely slide along that tracks:

I’m trying to find a low profile way to ensure that whenever the cut in the moving block faces upward vertically, the block is pushed up (almost) touching the inner face of the ring. That is, it returns to its “home position” whenever the cut faces up:

The block is just driven by a crank. Indeed, the crank can freely shift vertically. However, i’m hoping the block (along with the crank) to return to the home position whenever the cut points upwards.

The only way I could think of is to have a part like a leg sticking out from the bottom of the block so that it pushes against the ring or an external track (near the bottom of the ring) whenever the cut nears facing upward. The issue is that this leg will require quite a bit of extra space, e.g., when the cut faces down but the block is at the top, the leg will point upward. The method should not constrain the block’s movement along the tracks or rotation.

Does anyone know of a better way?

Any thought appreciated.