Terrible i5-8400 Performance - We Finally Figured It Out!

Have any of you experienced this type of throttling with a B360 motherboard with your i5’s? We tested both i5-8400 & i5-8600K and replicated the results no matter what we adjusted. Actual PC specs are below. • i5-8400: • i5-8600K: • MSI B360M Mortar Titanium: • ASUS Z370 Prime: • Corsair Vengeance Pro RGB DDR4-3200 2x8GB: • DeepCool Gammaxx GT CPU Cooler: • Palit G