"With 11 days of rest, Misiorowski threw a simulated game and a bullpen session. That’s when pitching coach Chris Hook and pitching coordinator Jim Henderson believe they found two mechanical flaws that were causing the lack of late life and “hop” to his fastball. You can see a video breakdown of those flaws above.."
https://www.si.com/mlb/world-series/brewers-solve-jacob-misiorowski-fastball-world-series-rays