Print Upright. Consider Using a Brim.
Hex Part has 13.45mm "key width".
Remix from here:
https://cad.onshape.com/documents/6fa60582e246890481f9a2f8/w/b73bd1c361b86bd48dfe38df/e/630f60caf197dab8c8dee008?renderMode=0&uiState=671cd443607c8a0707146358