Mock Exams Error Clustering always, totally, elsewhere

LokiDog2

Folks, in mock exams, are your errors generally clustered in few vignettes or spread across the entire exam?
I always have 2 or 3 vignettes out of 10 that I almost totally blow off (5/6 wrong) and very few errors elsewhere. I’m scoring around 70% +/-5%.
I think this is bad as it increases the volatility of results. What is the best strategy? Do you go back to books and re-read? Qbank? or simply read the answers and move on?