Impossible generation with 5 courses - One less and it works

[infoo_]

Hello

I attach you a fet file regarding 5 courses.

This file has the least valid constraints, such as min days between same acts (by general rule, a subject cannot be taught the same day more than 2 hours), Students max gaps per week, Students set min hours daily and Teacher not available.

I started trying activating 1C acts and it works. Added 2C, it works. So on and so forth, when I activate 5C it stucks at 121/122 acts. If I deactivate 2C (and keep active 1C,3C,4C,5C), it works.

I tried deactivating one course at a time, and it works. I tried some pair of courses, but I cannot understand what's going on (maybe I did not found the bug).

It is very strange, I don't know why 5 courses don't work - but deactivating one of them it works.

Thank you!!