During COVID in UK alot of grades were given by teacher assessment not by an exam. There was grade inflation. For one reason I didn't see was, people mess up ex

During COVID in UK alot of grades were given by teacher assessment not by an exam. There was grade inflation. For one reason I didn't see was, people mess up exams, run out of time, spend too much time on an answer, misread a question, panic, don't turn over a page, feel ill on the day. Predictied grades don't predict non knowledge based exam performance. I wonder have there been studies covering how many grades are lost due to such failings.