Molten Strike (poison) + Anomalous Returning Projectiles - Performance Issue

While delving on my Poison Molten Strike + Anomalous Returning Projectiles Pathfinder, I started experiencing noticable lag that induced several deaths.

This only happened once I'd reached a depth of around 700-750+ where I suspect mob HP got too high to easily calculate the poison damage thus causing an incredible slow-down lag. This only happened in a multi-enemy environment.

I never experienced this in a single-target encounter.
I never experienced this during T16 high density mapping.

I tested this WITH and WITHOUT Anomalous Returning Projectiles socketed.

WITH Anomalous Returning Projectiles socketed (big lag):
Example 1: https://youtu.be/1t_4eoDOZKs
Example 2: https://youtu.be/b5vmkixRVqA
Example 3: https://youtu.be/vX4os4wzL7g

WITHOUT Anomalous Returning Projectiles socketed (no lag):
Example 1: https://youtu.be/x43WhkuWd20

I also tried Nimis. No lag. Unfortunately no video evidence of that.

My theory is that it's got something to do with the extra 20% chance to return again on Anomalous Returning Proj, but I didn't test a regular version of the gem as this is a hindsight thought and don't have some of the gear anymore to test it.

You can view a snapshot of my character at that time here if you wish to try replicate: https://poe.ninja/builds/ancestor/character/miumiubaby/dmerc_justflaskthings?time-machine=week-6