Often disgruntled teams are seen as a negative thing: people are unhappy, their productivity is low and they won't be willing to go the extra mile for their project.
A nice bag a lemons, don't you think?
How about turning those lemons into lemonade, then?
Disgruntled workers are great agents of change. They are unhappy about they way things are now in the project. This means they will be more open to new ways of working.
Maybe they are unhappy because they feel isolated and not informed about the rest of the project. A project management tool where everyone can contribute and know what's happening can be presented to the team as a way to get the information they so crave.
Maybe the team feels overworked and thinks management is insensitive to their needs. With a project management tool's time tracking features, they will be able to prove how much they are working on their projects. They can even track how accurate time estimates are to complete their tasks.
On the one hand, you have a team working with a tool that can help them solve their problems. On the other hand, you get metrics from the project management system, so you can prove them right (or wrong).
Harness the energy
When people are unhappy about something, their negative energy (lemons) can be turned into a drive for change (lemonade). And people who feel they have some control over their environment are generally happier in their jobs.
And happy people work more, better and smarter.