To help Ava finding her way through the blocks of concrete, Jillian Salvius gives her a GPS tracker.
Since GPS trackers need a clear view of satellites to work, they would not be of any use within 10ft of concrete.
While reading the Warrior Nun's journal, Sister Beatrice pronounces lieutenant the American way (lew-tenant). She is British, and the usual pronunciation is left-tenant, however some pronounce it 'Lew'tenant, recognising the word's French origins.