The noble disciple has faith in the Dhamma (the teachings), including in the truth of the Dhamma, and also takes refuge in the Dhamma.
"He (the noble disciple) possesses unwavering faith in
the Dhamma thus: 'Well propounded by
the Blessed One is the Dhamma, evident, timeless, inviting
investigation, leading to emancipation, to be comprehended by the
wise, each for himself.'
A Dhamma follower accepts the Dhamma only after learning it, and reflecting upon it.
“What kind of person is a Dhamma-follower? ... but those teachings
proclaimed by the Tathāgata are accepted by him after reflecting on
them sufficiently with wisdom. Furthermore, he has these qualities:
the faith faculty, the energy faculty, the mindfulness faculty, the
concentration faculty, and the wisdom faculty. This kind of person is
called a Dhamma-follower.
But the Tipitaka is not the same as the Dhamma.
Monks and lay followers don't consider the Tipitaka infallible or incorruptible. The words of the Buddha as written in the suttas are not considered the verbatim words of the Buddha, as they may have been paraphrased for ease of memorization (please see this answer for details). Furthermore, the Buddha did not speak Pali. Rather he spoke Prakrit dialects similar to it.
The meaning is more important than the phrasing:
The venerable ones agree about the meaning but differ about the
phrasing. The venerable ones should know that it is for this reason
that there is agreement about the meaning but difference about the
phrasing. But the phrasing is a mere trifle. Let the venerable ones
not fall into a dispute over a mere trifle.’
Sometimes, later additions to the Tipitaka are acknowledged by the Tipitaka commentaries. You can probably consider them counterfeit, but they are few and insignificant.
There may also be minor contradictions between some suttas.
The most important point is that the Dhamma can be understood from a significantly large part of the Tipitaka. All of the Tipitaka are not true or useful, but all of the Dhamma is true and useful.
But none of it is unjust.
From the book "The Authenticity of the Early Buddhist Texts" by Ven. Sujato and Ven. Brahmali:
Both the EBTs (Early Buddhist Texts) and the later tradition, then,
quite readily acknowledge that some discourses were not spoken by the
Buddha. In some cases, such as the final verses of the Mahāparinibbāna
Sutta, this could not have been otherwise, as the context is after the
Buddha’s passing away. In other cases, however, such as the verses of
the Lakkhaṇa Sutta, even though the Sutta features the Buddha himself,
the commentary is still happy to acknowledge that the verse were added
later. The fact, therefore, that in the majority of cases there is no
acknowledgement of lateness tends to authenticate these text as having
the historical Buddha as their origin.
Also from section 4.4.1 of the same book:
These episodes, and others, could easily have been edited out, but
they were kept despite their awkwardness and their not fitting with
later ideas. This indicates that the attitude towards preserving the
EBT was very conservative.