आगमे शैवे विश्वासटिप्पन्यः

Source: TW

A Guru or Ācārya doesn’t have to be omniscient to impart potent metaphysical truths.
He can, in fact, be wrong about historical or other factual issues and yet be able to impart spiritual statements which are potent and can lead one to an obtainable Ādhyātmika end.
There is also no connection between a Guru’s mantrasiddhi and his accuracy in both laukika and atilaukika matters. A guru can have animādi siddhis and still be parviscient.
What enables a Guruparampara to transmit metaphysical truths in an unbroken and intact manner, preserving their spiritual potency for their respective seekers, is Śiva’s/Īśvara’s anugraha. You can have a line of parviscient teachers who flawlessly preserve a certain doctrine and yet can be dead wrong about history of their institution or even basic empirical facts, etc—because it’s Śiva’s limitless grace that endows this transmission with potency, provided that they adhere to the vidhis applicable to them without breakage—brahmacarya, ācāra, śīla (conduct), etc.
Likewise, an institution can have ignoble, confused, controversial or even usurpative origins & yet produce great Gurus/Siddhas, who are able to impart potent teachings and lead their followers to appropriate ends, even from the beyond—This is because it is Śiva who graces this to happen at the right time, allowing the proliferation of Siddhas from a particular guruparampara, no matter their imperfections or defects, with consideration to what certain souls need at that time.

May Śiva bless all of us with Gurubhakti that is subservient to Īśvara/Śāstra bhakti and ever subordinate to the desire for truth (satyakāma) on this Guruvāra.