try downgrading to Katalo Studio v7.9.1
You can download it at
Why? Katalon Studio v8.x included several changes internally. That caused several performance problems but they have fixed them. For example, see
If you find v7.9.x is better, your case may suggest KS v8.2.x has one more problem unresolved.
In that case, you should talk to Katalon Team and request their investigation. If you are using a paid license, you should submit an official support ticket. They would ask you to provide a zip of your katalon project. Let them have it and wait.