Jordan got 'stuck', the first 5-6 books came out near yearly, then the later ones took comparatively ages while the quality declined due to him having too many characters and having to move people around to get them into the positions he needed at the right times which left half the cast treading water plot wise at any given time but still getting chapters- near exactly the same problem Martin's Song of Ice and Fire has battled for the last decade, though at this point Martin's just taking the piss. Pretty sure the 'recap' type chapters were added to the later books to make sure existing readers remembered what happened 2+ years ago when the last book released rather than for new readers, but they definitely hindered the already glacial pacing even more.
It wasn't so much he got "stuck" as he was technically dealing with a life-affecting disease, which actually did result in his death. That was one of the reasons the writing got slowed down by so much, he was dividing his time between actually writing the story, and making sure there were details and explanations for how the story should go if/when he died before completing it.
Apparently, he did make a couple of raaather large spreadsheets detailing characters, arcs, appearances in previous books, plots and subplots they were involved in, etc. Along with copious notes on the world and cultures.
Although he did get a wee bit irritated over fans who kept moaning about Matt being "missing" from most of one book - he was all "The previous book ended with a rather large wall falling on him and injuries resulting from it. I didn't think anyone would be that interested in large chapters involving Matt covered in bandages, laid in bed, sleeping and recovering and not doing anything actually story affecting."