contract always states: for those damages due to your negligence, you have to replace the same with new ones at your own cost and expense and to yield up the same in good order and condition at the termination of the tenancy.
So if 房东一口咬定是我们‘操作不规范’造成的, then you have to find sth to prove it is wrong.
my ex-房东 is an A/P from NUS, he is that kind of 房东. I am still arguing with him and his wife which is also that kind....