Just solved the deadlock! I’m currently using the p-limit package to limit the number of concurrent actions made to the website source. Basically, inside a function wrapped by that limitation, I was waiting for another function that would require the limit to be complete! Of course, that would create a never-ending deadlock. Fixed now!
On a second thought: I don’t actually like the structure of the internal code I use to process all of this. Maybe I should rearrange some things to make them… better.
Or if you don't know what a response is, you can always write a webmention comment (you don't need to know what that is).