It just happened to my pt, we did 3 runs and all them with the bug. The tomberris didnt die, no matter what.

Time: 12:30am GMT +1
Frequency: 3 times in a row
World name: Ragnarok
Character name: Skuld Veil
NPC name: NA
Monster name: Tonbery
Class/Level: Level 50 Bard
Party or solo: Party of 4