Sola scriptura is a neat doctrine, because it provides the believer with absolute surety. “Jesus loves me; this I know, because the
Bible tells me so,” as the Sunday School song goes.
The biggest problem with the doctrine is that the
text itself argues against an inerrantist reading. How many angels were at the empty tomb: one or two? Who was at the empty tomb? Who was at the Crucifixion? How many times did Jesus visit the temple?
The Gospels differ. This happens a lot throughout Scripture, especially in the parallel histories of the OT (Samuel/Kings/Chronicles). Protestants tend to feel a desperate need to explain away these differences, because they want to believe that Scripture is inerrant. Nonetheless, the differences are there, and they are quite obvious to anyone who looks for them.
There are two possible reasons for including these different accounts: either the compilers of the
Bible did not notice the differences, or they did not care about them. Considering the fact that we are talking about one of the most literary cultures in the history of the world, the first option is not at all a good one. The most likely reason is that the compilers of the
Bible knew about the differences and were utterly unbothered about them. This is most probably because they did not see the texts as literally true, and, therefore, there was no “contradiction”.
Of course, should you tell a Protestant this, you risk shattering his/her faith entirely, which is not a good idea. So, what I would like to suggest is that you could research some of these differences and talk with the Protestants about them. You could also talk about the fact that the Catholic Church uses other texts from the succeeding centuries to develop a better historical understanding of the situation. For example, most Protestants believe that Mary had other children, whereas Catholics take a view which is
supported by documents from as early as the C2nd, and which does not contradict the Gospels in any way. For this point, you could see also my posts
here, because I
disbelieved the Catholic position at the beginning, only to research it and find that, from a historical perspective, it is far more dependable than the Protestant one.