"Namharim, First of the Night" permanent immortality

This has happened to me a couple times already. The "yellow/Vivid" seed boss "Namharim, First of the Night" just stops taking damage when the HP bar reaches around 2/3rds. Other Harvest bosses function just fine.
This is not just an issue with the harvest encounter version, but can also happen with the map boss version.

encountered this issue several times this league already with a volcanik slam warcry berserker.

Sometimes leaving the map and reentering fixes the boss, sometimes it doesnt. in the reported bugreport it did not (reentering the harvest did not fix it either) and i was forced to abandon the fight as it was still bugged after 3 minutes of continuous combat.