when somebody/something falls or slips through the cracks, an organization or a system fails to find them and deal with them跌倒/滑入裂缝：当某人/某物跌落或滑入裂缝时，组织或系统无法找到并应对它们
We tried to contact all former students, but one or two slipped through the cracks.我们试图联系所有以前的学生，但一两个人漏掉了。