I dunno which part of this can be considered as bug, so let me explain this. Additional battle task “Kill 5 enemies with hand grenades” can be completed with hand grenades as intended, but also with TNT Sticks. So:
- Task description is outdated and it should be somethng like “Kill 5 enemies with throwable explosives”?
- Game code is bugged and its counting not only grenades, but also TNTs.
Take your pick.