Swift advice please

Hi, I need some advice please. I have had returning Swifts to nest in my house for a good number of years now. However, it seems I have, I think , 2 juveniles attempting to gain a new access.

Unfortunately on Sunday, they somehow managed to collide knocking one down into my cat infested garden. After a little rest, he took off again. I witnessed the same thing happen again on Monday, this time thankfully, managed to recover its wigs without hitting the ground.

Do you think I should look to having a box installed for them or is it too late - dilemma!