Yes you have to be careful with renewal.
One big insurer i used to be with that advertises how much money they save people just discontinued the accidental damage component of our house insurance.
We had a gust of wind grab the back dual glass doors (that had been left ajar) and damage them.
When we went to see if it was worth lodging a claim the insurer just said "we took accidental damage out of your policy in your renewal".
Ended up fixing myself after some research but i would have thought they would have an obligation to specifically inform you of such a big change.

