Killing a Harmonizer sometimes makes surrounding Sifters unkillable

I done multiple Harmonizer battles throughout my run, and after I kill the mini-boss, the surrounding Sifters (commonly Seedlings and Sentinels) will get permanent fast healing buffs when they are “Enraged,” making them practically invincible, regardless of weapon or power level, forcing me to knock them off cliffs.

Steps to Replicate:

1. Initiate any Harmonizer mini-boss fight or ambush (preferably through a rift).

2. Defeat the Harmonizer with some living Sifters in radius that can be “Enraged” upon the mini-boss' death.

3. Some of the Sifters cannot be killed and heal indefinitely (this does not happen every time); in addition, their hp never fully drains when dealt otherwise fatal blows.

P.S., if this is an intended feature, please confirm.