I have a flat rubber roof that leaks very badly when it snows and then
rains. It happened twice this year during two storms between Feb and
March. The weight of the snow and rain somehow must pull the rubber
away from where it should cover the roof from the outside elements.
When it rains hard it never leaks.

There is a vent pipe and a square opening with cover (to gain access)
near the leak.

Any ideas on what to do?

CP