@tatut perhaps you can try profiling the process when it is doing this?
I’d run the visualvm cpu sampling and then open the “hot spots” panel. Then find some of the top ones and “expand” to those call sites. You could even share the nps file for someone like me to look at - but that may not be good if it’s proprietary stuff.
I can try
I couldn’t make heads or tails out of visualvm sampling
something weird is definitely going on, initial build 20s (startup after deleting all compiled files), then successive watcher builds after editing a very simple file (containing a single component that has just a div with text): 28s, 15s, 16s