Unloading package in one block does not affect the next block

Haha :joy:

Earlier this year I happened to have written a blog post on caching: https://yihui.name/en/2018/06/cache-invalidation/ It is not impossible that you could waste more human time when trying to save some computer time with caching (the cost of understanding caching could be high). Well, in your case, you can just blame the surprising behavior of knitr's caching on me.