As a result of some serious Prolog programming exploiting recent features such as $/0, unification that gets inlined into the head and =>/2 rules I’ve pushed a number of enhancement to the debugger. If you use this stuff and do debugging it might be wise to update by pulling the git or using the daily builds for Windows (as of tomorrow).
I’ve also tried to address xpce/X11 issues that cause the debugger to start really slowly. I made some progress. The real cause of this remains mostly a mystery 
If you build from source you’ll get an error on incremental build in xpce. Either build in a clean directory or run the command below before running ninja (or make).
rm packages/xpce/h/names.i?