1Ne 1:4 For it came to pass in the commencement of the first year of the reign of
Zedekiah, king of Judah, (my father, Lehi, having dwelt at Jerusalem in all his days); and in that same year there came many prophets, prophesying unto the people that they must repent, or the great city Jerusalem must be destroyed.
First point: Jeremiah was the contemporary prophet of Nephi.
Jer 1:1 ¶ The words of Jeremiah the son of Hilkiah, of the priests that were in Anathoth in the land of Benjamin:
2 To whom the word of the LORD came in the days of Josiah the son of Amon king of Judah, in the thirteenth year of his reign.
3 It came also in the days of Jehoiakim the son of Josiah king of Judah, unto the end of the eleventh year of
Zedekiah the son of Josiah
king of Judah, unto the carrying away of Jerusalem captive in the fifth month.
4 ¶ Then the word of the LORD came unto me, saying,
5 Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and I ordained thee a prophet unto the nations.
================================
First point of Disagreement
================================
Nephi depicts all the prophets preaching against the sin of the people, while Jeremiah depicts God having kept the coming wrath from the prophets except for Jeremiah. I.e. the question is, which account is correct?
1Ne 1:4 For it came to pass in the commencement of the first year of the reign of Zedekiah, king of Judah, (my father, Lehi, having dwelt at Jerusalem in all his days); and in that same year there came many prophets, prophesying unto the people that they must repent, or the great city Jerusalem must be destroyed.
Jer 4:6 Set up the standard toward Zion: retire, stay not: for I will bring evil from the north, and a great destruction.
7 The lion is come up from his thicket, and the destroyer of the Gentiles is on his way; he is gone forth from his place to make thy land desolate; and thy cities shall be laid waste, without an inhabitant.
8 For this gird you with sackcloth, lament and howl: for the fierce anger of the LORD is not turned back from us.
9 And it shall come to pass at that day, saith the LORD, that the heart of the king shall perish, and the heart of the princes; and the priests shall be astonished, and the prophets shall wonder.
10 Then said I, Ah, Lord GOD! surely thou hast greatly deceived this people and Jerusalem, saying, Ye shall have peace; whereas the sword reacheth unto the soul.
For more references see Jeremiah 5:31, Jeremiah 14:14, Jeremiah 23:16, Jeremiah 23:25
.
Another main disagreement is that Nephi is written in the first person and uses his father as a reference and Jeremiah is written in the third person and uses God as a reference.
.
The final point I'll bring up for now is that the God Jeremiah was talking to said "do not go into egypt" but the God Nephi was talking to said to go into Egypt, which God was correct?
1 Nephi 5:15 And they were also led out of captivity and out of the land of Egypt, by that same God who had preserved them.
Jer 42:19 The LORD hath said concerning you, O ye remnant of Judah; Go ye not into Egypt: know certainly that I have admonished you this day.
Jer 43:2 Then spake Azariah the son of Hoshaiah, and Johanan the son of Kareah, and all the proud men, saying unto Jeremiah, Thou speakest falsely: the LORD our God hath not sent thee to say, Go not into Egypt to sojourn there:
These are the issues I typically encounter when reading the book of Mormon.