Yes, I've created a thread on this very problem and done my best to go through it in detail, you can get it to work but it is currently very fiddly, I think unnecessarily so.
https://godotforums.org/d/31289-investigating-the-floating-navmesh-agent-behaviour-and-fixing-it-for-good/14
I'm convinced that the issue is the max slope variable is too low, it would be great if we could have some add on or whatnot implemented to remove the limit and test things. If it bothers the back end devs they should just have a little warning pop up or something so people know something might break.
I would like to make a bit of noise about this.