Tradução de "slip through the cracks"

Olá.

Tentei, tentei bastante, mas não encontrei uma equivalencia dessa frase em portugues. Achei achei a explicação e um exemplo, mas realmente, não saberia como utilizá-la.

to slip through the cracks – to not do something through neglect; to not payattention to something, usually because one was busy doing other things
Exemplo: I was so busy working on these essays that somehow the math assignment slipped through the cracks and I forgot to do it.
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Avatar do usuário Donay Mendonça 49135 21 73 1140
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Avatar do usuário Thomas 14290 7 58 283
It can also mean "to fail to meet the requirements for technical reasons".

I had a client who was too crazy to be in jail but too well to be in a psychiatric hospital. He slipped through the cracks.

A friend, as a child, wanted to join a youth group that required the participation of both parents. He lived with his father, but his mother was dead. His request for membership was refused and he slipped through the cracks. Twenty years later he was still bitter, and I understand perfectly.

An American student, who spoke Portuguese, applied for a student visit to Brazil offered by the Rotary International. The club sponsoring the trip was very pleased with the student's application, but he lived outside the club's zone and there was no such program in the area where the student lived. He was not sent to Brazil. He slipped through the cracks.
Obrigado a todos.

Acho que : Passar batido se encaixa bem ai.

Muito obrigado!!!!!
E como vocês traduziram as sentenças compartilhadas pelo Thomas?

I had a client who was too crazy to be in jail but too well to be in a psychiatric hospital. He slipped through the cracks.

A friend, as a child, wanted to join a youth group that required the participation of both parents. He lived with his father, but his mother was dead. His request for membership was refused and he slipped through the cracks. Twenty years later he was still bitter, and I understand perfectly.

An American student, who spoke Portuguese, applied for a student visit to Brazil offered by the Rotary International. The club sponsoring the trip was very pleased with the student's application, but he lived outside the club's zone and there was no such program in the area where the student lived. He was not sent to Brazil. He slipped through the cracks.

Fiquei sem entender a expressão idiomática nos contextos acima!