...such care, he or she will be deemed to be contributorily negligent even though the negligence of the employer was also a contributing cause of the injury. The...
... for a better answer. 不可歸咎於某人的疏失、過錯 The negligence or mistake that can not be pinned on sb to neglect (verb)疏失/疏忽的動詞...
Paraphrasing it: We are terribly sorry for the inconvenience caused by our staff's negligence this morning. We sincerely ask for your forgiveness and thank you for your understanding.