Enemies in Expedition sometimes completely immune to Ignite, despite not being immune to Fire

I have encountered a bug with expedition enemies becoming completely immune to burning. At first I thought I might've clipped a "immune to fire/chaos" node, but that is not the case.
In the video linked below, I tried to kill enemies with Chaos Incinerate (Blackflame ring), but they take no damage. Then I remove the ring and try to damage them with regular Incinerate - no damage either. Then I use Flameblast and Ember Fusillade (both dealing fire damage, of course) and enemies take damage as expected.
https://www.youtube.com/watch?v=gcy_eUAZzSQ