Contradiction with Genesis 38:7
It describes Er, the firstborn of Judah, as wicked and killed by God, which seems to counter the notion of his lineage discussed in Numbers 26:19.
Genesis 38:7: And Er, Judah's firstborn, was wicked in the sight of the LORD; and the LORD slew him.
Contradiction with Genesis 46:12
This passage provides a genealogy that includes Er as deceased, contradicting the listing in Numbers of Er having potential lineage.
Genesis 46:12: And the sons of Judah; Er, and Onan, and Shelah, and Pharez, and Zerah: but Er and Onan died in the land of Canaan. And the sons of Pharez were Hezron and Hamul.
Contradiction with 1 Chronicles 2:3
Er is again mentioned as wicked and dead, contradicting his mention in the context of Numbers 26:19's genealogical listing.
1 Chronicles 2:3: The sons of Judah; Er, and Onan, and Shelah: [which] three were born unto him of the daughter of Shua the Canaanitess. And Er, the firstborn of Judah, was evil in the sight of the LORD; and he slew him.