Serverless worker failing - how do I stop it

I have a couple of questions. I use Runpod Serverless to power a ComfyUI API - it works well most of the time but today I noticed one of my serverless workers kept failing. The errors only occured with one of the workers, the others performed fine. Why would this be? and is there a way of terminating specific workers? also, how can I get notified if one of them is playing up?

Thanks!