One of the covenant-breakers says: ‘Infallibility belonged to Baha'u'llah alone; no other person is infallible.’

One of them [Covenant-breakers] saith: ‘[Bahá’u’lláh] hath made us independent of aught else, and hath left no need unmet.’ The secret intent of such a statement is that there is no need for an appointed Centre. Another exclaimeth: ‘Infallibility belonged to [Bahá’u’lláh] alone; no other person is infallible.’ His inner motive is to assert that [‘Abdu’l-Bahá] is liable to error. Furthermore, they say that one who was regarded with favour, who was a believer or the recipient of a Tablet during the days of [Bahá’u’lláh], cannot possibly be cast out. Their true objective is to hint that were such a person to arise in opposition, or be so bold as to show enmity, no harm would result.... The whole purpose of these words is to violate the Covenant and Testament.

(The World of the Baha'i Faith, Edited by Robert H. Stockman, p. 417)

https://www.routledge.com/The-World-of-the-Bahai-Faith/Stockman/p/book/9781032186078