Of course it was, but no more so than the OT texts. In many cases, less so, since the OT texts are much, much older and had already been redacted by the time the church got hold of them and further edited them as they did the NT texts.
The OT can be compared to the Septuagint Tanakh, no such classic standard exists for the NT.
Take a comparison of the NIV and KJV NT books, major wording difference, in some cases complete verses missing.
The oldest complete NT we have is the Vulgate which is unchanged from the original vulgate. If the bible NT were unchanged there would be far less resentment against catholics and everyone would be following catholicism.