Vaal Foundry Map Boss Lava Damage

Played Maps and got the Vaal Foundry Boss.
After death the damage scaling of the lava carried over to following tries (same instance) resulting in instant deaths.

Try 1 Die because too long in lava (20 seconds maybe)
Try 2 died touching the lava for only a very short time <1sec
Try 3 & 4 died instantly touching the lava.

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