This is a review of the remaining bugs on the encounter with the Blast furnace.
Phase one:
http://www.wowhead.com/npc=88821/bellows-operator
"Increases the Heart of the Mountain's Heat levels; once Regulators die, Operators must be tanked, and will use http://www.wowhead.com/spell=177756/deafening-roar "
When the heat regulator is destroyed, the operator still increasing the heat level
"As long as Regulators are alive, Bellows Operators are not affected by the Security Guards http://www.wowhead.com/spell=160382/defense "
Operators are affected by defense buff while the heat regulator still alive.
Phase 2
In the begining of the phase, two slag elementals are spawned instead of one
"Note that Primal Elementalists are immune to the damage-reduction portion of http://www.wowhead.com/spell=160382/defense "
Primal elementalist are affected by http://www.wowhead.com/spell=160382/defense when they shouldn't
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This is a bug that sometimes happends:
When there is a server shutdown, disconecction or reset, sometimes the blast furnace spawns again even if you have finished the encounter the day before. I'm not talking about the IDs reset, I mean, for example, if you kill the blast furnace on thursday, it's possible that on Friday or Saturday or another randon day before Wednesday, the boss is spawned again, with the foreman and all the stuff like you haven't defeat him. This happends sometimes to oregorger, I only have seen this one time on this last boss. We realize the bug of the blast furnace 5 days ago, It can be related with the implementation of the Flamebender
Source where I found the bugs: http://www.wowhead.com/guides/raiding/blackrock-foundry/blast-furnace-strategy-guide
Just to remember there is another bug in Blast Furnace :p
Link : https://firestorm-servers.com/fr/report/see_report/2892
(It concerns the guards in P2)