The phrase "letted fall between cracks" refers to something that has been overlooked or neglected. The word "letted" is an archaic form of "let" meaning "allowed" or "permitted" in the past tense. Its pronunciation is /ˈlɛtɪd/. The phrase implies that something has been allowed to fall between the gaps or cracks unnoticed. It serves as a cautionary reminder to pay attention to the details, so nothing significant goes unnoticed or ignored.