[Akame]

The insulated hilt makes you lose 5% lightning RES instead of gaining it.
Edit: Either that, or you don't gain any resistance at all. I should have 29% but I get no 'green text'.

[Neus]

Check the damage resistance player debug. It'll show up as Customization Dres.

[Akame]

Debug: Checking resistance effects and listing them below for 100 Lightning damage with a bonus of 0% resistance.
Resist Okay? Yes--------------------------
Artificial Body; 0
Mercalan Mist; 0
Pure Fire; 8
Hard Light; 8
Quest Stamps; 8
Golden Glow; 8
Monster Elemental Affinity; 8
Customization Dres; 8
Item el_res() and sayakana; 24
Elemental Weakness Status; 24
Bonus Resistance; 24
Elem Mod Status Effects; 24

----
Here it is.
For reference;
I am wearing a 11% Lightning RES ComC
8% lightning res from SAN
5% lightning res from sayakana
5% lightning res supposedly from insulated hilt

[Neus]

This should be corrected.