Re-leaning Esperanto on lernu!

I read the chapter #1, #2 and #3 of the course “La teorio Nakamura”. I’ve already learned them before though, they were so helpful since I forgot some words and pronunciations.

Practicing Spanish roll-ed R

As the pronunciation of R on lernu! is so rolled, practiced how to roll R with reference to How to roll your R’s: The definitive guide for a bit.
But after practicing that, I noticed some R’s were rolled and some R’s were not rolled. What’s the difference about that? There was no informations on lernu!.

【呪印感染】 Q熱感染・白 (途中セーブ)