Spell penetration value changing with no clear reason?

DTStormfox

For no clear reason, my spell penetration value seems to be jumping from 5978 to 8952 and back. Am I missing something here? Is this a visual bug?

https://youtu.be/xnphzrekwMs

Some info:

Server: EU
Arena: no-cp, no-proc Cyrodiil
Class: Nightblade
Race: High Elf
Vampire/Werewolf: No
Mundus stones: The Apprentice & The Shadow
Gear: 5x Twice-born Star, 5x Amber Plasm, 2x Slimecraw
Weapon: Flame staff, sharpened trait, shock damage enchant
Abilities on bar: Reaper's Mark, Mass Hysteria, Swallow Soul, Merciless Resolve, Blinding Flare, Soul Tether.
Food/Drink: Witchmother's Potent Brew

SkadiMZ

You probably don't have the "prevent attacking innocents" option turned on in settings, so as NPCs walk by, it will increase your penetration by 2,974.

5,978 + 2,974 = 8,952

DTStormfox

Yes, it may have something to do with the Master Assassin passive. However, observe two things.

First, I don't 'aim' at any NPCs (or players) in the video and second, I have the "prevent attacking innocents" turned on.

SkadiMZ

Well, considering the values of penetration, it definitely has something to do with the master assassin passive, it's just a question of how the game evaluates when or if the penetration should be increased.

The "prevent attacking innocents" toggle may only prevent skills from firing, but seeing as how innocents can be attacked in certain situations, it probably makes more sense to have skills not fire instead of coding in situational context into every passive and skill.

Why not try to see if you can replicate this when you're in a player house without any target dummies, house guests or pets so that you can be sure the penetration is changing for no reason and isn't being influenced by NPCs or nearby players?