The saying about a stopped clock is "a stopped clock is right twice a day".
The saying "a stopped clock is right twice a day" means that even something or someone that is usually wrong or unreliable can be correct occasionally, even if it's only by chance or by accident.
It also highlights that nobody is wrong all the time and even a broken clock will display the correct time twice a day on a 12 hour clock.
A standard analog clock for example will show the correct time twice a day when the hands align with the current actual time of day or night.
The phrase a stopped clock is right twice a day is used to suggest that even a person that is frequently incorrect or unreliable can still offer a correct or insightful observation at some point.
And it's often used to point out that a one off correct statement or action does not necessarily mean that someone is reliable or knowledgeable.
Basically it's an expression that means that even something or someone that may normally be totally useless can sometimes make a valid point.