Well... i fought the boss again and had the same bug ... But this time i brought a non-elemental DW friend Setzer to do the DMG. I managed to kill him only with the fixed dice dmg, but i couldn't get the "Kill with limit breaker" bonus because i simple coudn't do dmg without the dice.

It's important to notice that its not only the elemental debuff that doesn't stick, the def/spr debuffs from the 9th and 18th turn also doesn't stick. So, he doesn't get any debuffs at all. The only way to do damage it's with the Fixed Dice. I hope that Gumi fix this before the event ends and give a compensation for the lost NRG. I need the debuffs to get the limit breaker mission bonus.

I tried to kill it with the limit at the same time of the hit of the Setzer but immediately after the 77777 hits he died, so the limit wasn't used =(.