Boolean problem

 From:  Buzhug
418.1 
Hello everybody.
I'm french (So, sorry for my english), and usually i work on Cinema4d.
I try Moi, and it's a real pleasure to model with. Congratulations for your job. And Thanks a lot to Steph3d and Pilou for their tutorials.
My first modelisation with Moi :
http://jipsou.free.fr/moi/MoiTest01.jpg
And render in Cinema4d :
http://jipsou.free.fr/moi/MoiTest01b.jpg

Now, I involve myself to model with Moi with a caliper :
The start :
http://jipsou.free.fr/moi/PiedCoulisse02o.jpg

But i have a problem. I would like to make a boolean like this :
http://jipsou.free.fr/moi/piedboolprob.jpg
The boolean diff between the gray object and yellow object.
Usually the boolean works great, but here, nothing. It don't work.
Is it a bug of the software or me ? Or is it normal ?
Thanks.

EDITED: 9 May 2020 by FINEMA