When in operator mode, your inactive frames are normally invulnerable, but receive only 90% DR if they have active abilities. This makes sense for abilities with continuing effects, such as Oberon's Renewal healing allies or Mesa's Shooting Gallery disarming enemies. However, this loss of invulnerability also applies to most defensive abilities that a frame might have active, such as Mesa's Shatter Shield, Ember's Immolation, Trinity's Link, Titania's Razorwing, Saryn's Molt, and Rhino's Iron Skin, as well as to abilities that are irrelevant while inactive like Excalibur's Exalted Blade, Saryn