well after restarting c4d, it stopped doing this. Currently IPR is working, until next time
yeah well in fact I got to tap several time randomly between the "Send and restart render", the "restart render" and the "pause render" buttons, and at stop point it stops looping freneticaly during the very first render iterations and actually render the image correctly.
EDIT 2 : I think I found the right process in order to prevent this IPR short looping bug, I first launch the green wheel, it starts looping, I then pause the render, wait 1/2 secondes and hit de arrows restart render button, and then I got my updated render. That just need a small script x)