Thanks for the new update Liviu. I've tested all of my difficult files and they all work well.
Thank you, Bobby, for the report! Actually, since you do not use rooms, I expect that the random seeds (and generation times, and final timetables) in your case remain the same.
I actually did a small script on my computer, GNU/Linux script, attached. I just put all the files I have in the "input" directory (I put separately the files which require user confirmation regarding constraints which are ignored because of inactive activities) and let it run (sh script.sh). And you can do it again, if you change the random seed in the script.