Hello there, i'm new with R markdown and I don't undestand why sometimes it can create a pdf file, and sometimes it doesn't work
like, it works sometimes, and if I just add one letter, it doesn't work
a simple letter, not even with an accent or whatever
it doesn't even give me an error message, it just doesn't compile into the pdf, and also it randomly opens a "HTML preview" even if I hit "knit to PDF"
and that's really bad 
help would be appreciated much, thank you in advance