One feud that should have never arrived or come to be. It is the conflict between Koffi Olomide and Werrason. These two men should have done a duet or a duet album together back in the late 1990s or early 2000s like JB did with Papa Wemba.
Looking at this video makes me angry. 

It is funny  but it is also disgusting. I can understand Koffi Olomide having problems with likes of Kester Emeneya and Papa Wemba but why with Werrason. Why would Koffi and Werra get into a war. I mean Koffi and Werra were close during Wenge original era. If I am not mistaken, Koffi is a godfather of one of Werra's daughters. SMH, Koffi and Werra, why did you two had a fallout in the first place. SMH.

Can anyone explain to me and others what was the cause of the conflict between Koffi Olomide and Werrason?

Maybe Koffi had impregnated one of Werrason's dancers.

Anybody else with a better answer ??

Maybe Koffi had impregnated one of Werrason's dancers.

Anybody else with a better answer ??

I don't disagree with  your theories. It could also be due to Papa Wemba. Remember Papa Wemba was originally Team JB but maybe he had a soft for Werrason and Koffi got angry about that.

But, what about that time when Koffi visited La Zamba together with Fally ?.... maybe it's just a cultural norm to have beef

Yep. This is one of these beefs I never knew where it came from. Of course, in the mid-2000 they were both on top of the genre, so a collision had to happen. But I never understood the event that triggerred the beef.

Archos explained it here
http://congovibes.com/congolese-music/back-when-koffi-and-werra-were-great-friends/msg36380/#msg36380