I'm not totally certain this is a bug, but it seems very odd so I'm posting here.
3 Thunderstrikes give 2.5% E/N Def, and 1.25% Ranged Def.
6 Thunderstrikes give 2.5% Range Def & 1.25% Def E/N.
If this is accurate, do those totals stack or do they supplant (it would seem strange that slotting 6 Thunderstrikes actually reduces the bonus for E/N compared to 3)
Anyhow thought I'd throw that in there. Hope it helps