City of Montreal officials say no one is in danger, but for now the new system has been put on hold.
The Montreal fire department launched the system citywide last week, while police have been phasing it in. It was supposed to allow police and firefighters to communicate with each other more easily.
Richard Liebmann, an assistant director of the Montreal fire department, said the system was initially working well, but then something went wrong.
"Certain messages on an intermittent basis weren't getting through, either from the dispatch centre to the trucks and at one point from the trucks or the portable radios to the dispatch centre," Liebmann said.
Firefighters kept their old radios as a backup and there was no danger to the public, he said.
But Chris Ross, speaking for the firefighters' union, said some of the city's firefighters were concerned.
"It's a very large health and safety concern," he said.
"The communications are essential in the event of a fire. As the fire grows, we have to report that back to the dispatch centre in order to increase the alarms to get the trucks on scene."
The fire department said it's sticking with its old system until the company providing the new system can ensure it works perfectly. The police department is also keeping its old radios in place until the bugs are worked out.