This is an old topic so I don't expect it to be addressed, but I want to chime in anyway since I'm having the same problem. For anyone searching for this topic/a solution, I at least want them to know it isn't just them! Your hardware probably isn't broken, this appears to be a software problem.
With some effort, I found a new-in-box Adonit Pixel (in 2020) to use with my 5th gen iPad, based on several sources reporting that this is the only active stylus that would work for my iPad.
In using Sketchbook — an app specifically listed as compatible with all of the advanced active stylus features I got the Adonit Pixel for — I've found the same issues other people have. While technically it pairs, under Adonit Jolt, the behavior is unpredictable. In addition to pressure issues (which I suppose you can alter in the tool settings), more concerning is the dreaded wavy lines which I could get with any cheap/dumb stylus, and worst of all, it periodically just stops drawing altogether, often in the middle of a line. The dropped connection (or whatever it is) might be a fraction of a second, or it may be long enough that I force quit and restart the app, thereby losing all levels of undo etc.
I keep looking, and have even contacted Adonit to see if they have some suggestions, but I'm not finding solutions.
I like Sketchbook the most of all the Adonit Pixel "compatible" apps I've used, but it's too frustrating to use with the Pixel. I'd love to think someone somewhere has a solution, or maybe is even working on one, but since I've literally had people tell me I should just upgrade my iPad and get a Pencil (sure, a $1,000 solution sounds reasonable), I'm not holding out much hope.
But I'll keep looking anyway. 🙂
