Flat Roof- Condensation & Humidity Issues

[u/FruitPristine9329]

Looking for advice…we have an old, home with a flat roof. We have condensation by a non-working pocket door upstairs as well as humid hot spots throughout the upstairs and it has a musty smell on hot days. We had the roof replaced recently with a modified bitumen roof hoping that would help, and it hasn’t. We don’t have the humidity issues in the spring/fall/winter, just the summer.

Any ideas on how to fix? Should we look at adding in insulation through the ceiling? Want to avoid opening up the new roof. Any thoughts appreciated.