Is my managing agent keeping me in the dark about a known building issue?

Hi, I planned to sell my flat this year, but have only recently been told (by chance) that there is an existing issue within the buildings in the same development – i.e. the possibility of pipes, embedded within cement, leaking and causing extensive damage to the flats involved.

A few days later, my managing agent was in the building (he’ll be selling my flat). He seemed surprised that I knew about the pipe issue, but eventually described the situation as a “ticking time bomb”, as the issue had occurred 5-6 times in the same development over the past five years.

He told me it was nothing to worry about and said I wouldn’t need to mention the issue to prospective buyers. I’m not an expert, but surely that would be at least unethical, at worst illegal?

He also told me that any damage to the individual flats (i.e. new kitchens/bathrooms etc) would be covered under the building’s insurance. I hope that’s correct.

Also, shouldn’t our managing agent/management company have apprised all of the flat owners of the situation years ago and perhaps even have preempted the problem at an earlier stage, hopefully causing less disruption to both owners & tenants?

This is a very stressful situation, so any advice would be much appreciated.