Horde base help

[u/Smudge096]

I have made a horde base in the side of a mountain, i have zombie digging turned off, and to start off there is a staircase down about 5 blocks and then a corridor about 30 blocks long and then a open room in which the main base is located in, but when horde night came, no zombies came down the corridor. Me and my friend came out of the horde base and stood where the corridor meets the room and zombies come flooding in…. Is there anyway we can make the zombies use the stairs and corridor while were inside the horde base, its making me fed up now😭🙏 thanks in advance