NPC DoT spell keeps interrupting every tick

[Sateist]

Location: Nisse Lair
NPC in question: Tomte Shaman (level 12 ish)

Bug: after being hit by the Tomte Shaman DoT, I was not able to cast any spells any more, each tick of the DoT would reset my spell casting timer.
Attached image for reference.

I was able to heal myself once, because I resisted 1 tick.

Tomte Shaman was able to keep me poisoned without Line of Sight (he was one level below). Nothing I could do besides wait and die (I was solo) without mobs in the vicinity

[Karen]

This is how NPC DoTs always worked in this game.

[Vitty Jokic]

I'm told dots from pets are permanently interrupting casts on every tick. Think this is from underhill zealot, necro pet, and one of the cabalist pets. Could be similar issues from dots casted by dot classes like cabalist, mana mentalist, and bonedancer.

[Tyr]

title says it all