Problem Rmd chunks end delimiter

Hi everyone !

I'm having a bit of a hard time coming up with a solution to this problem, or either finding any related topics.

I can't explain why or when, but my Rmd chunks started not displaying the running buttons anymore. I cannot run them through Ctrl+Alt+Enter either. The first ones of my file seem ok, but at some point the option just disappears.
As you can see in the screenshot, the end delimiter isn't considered as such.

Also, the text under every chunk seems to be considered linked to the end delimiter, as when I hit the end delimiter arrow (left to the end delimited), the text rolls up.

I'm really wondering what I've done wrong.

Thanks for you help !