The term "un-erringly" itself implies perfection and absolute precision. Therefore, its antonyms describe imprecision, inaccuracy, and inconsistency. Words such as "mistakenly," "incorrectly," "falteringly," "imprecisely," and "indiscriminately" can be used as antonyms for "un-erringly." These antonyms signify a lack of accuracy, flawlessness, or perfection, and instead suggest a level of uncertainty, error, or mistake. In short, the antonyms for "un-erringly" are words that are associated with imperfection, fallibility, and inaccuracy.