Double tapped breakers are when two wires share a single breaker. It’s only a problem when the breaker is not rated or designed for two wires to share that one breaker. If the issue is left unresolved, then the connections could become loosened over time and may result in arcing or a potential fire.
The correction: This is easily corrected by a licensed electrician.
One option might be a pigtail connection, this works fine as long as the breaker isn’t overloaded.
Another option: If the breaker is being overloaded then there should be another breaker added on, as long as there is room to do this.
Another option: Adding in a tandem breaker as long as the manufacturer of the panel allows tandem breakers.
Double tapping, although it may lead to significant problems if the connections become loose over time, it is a common and easy issue for licensed electricians to correct.