When we first see Ensign Ballard, she fires on the ship pursuing her. The disabled ship grinds to a halt, instead of continuing to glide through the vacuum of space, as it should.
Ensign Ballard didn't know that Tuvok had been promoted to Lieutenant Commander until this episode, but she says she was killed by a Hirogen hunting party. Tuvok was promoted early in season 4 ("Revulsion"), but the Hirogen were not met until later in the season ("Message in a Bottle"), so Ballard should have known about Tuvok's promotion prior to her death.
When the twins Rebi and Azan explain to Seven that they have made cubes out of their clay, one of them mentions that they are one-one-thousandth the size of a Borg vessel. The cubes are clearly only a few inches square. One thousand times those dimensions would be only a few hundred feet, and one thousand times the volume would only be about 50 feet square, clearly much smaller than all Borg cubes seen in all Star Trek series. A more likely description would be one-ten-thousandth the size of the Borg cube.
It is mentioned several times that Ensign Ballard died three years ago; however, the stardate of her death, 51563, suggests that she has been away only for a little over two years.
When Ensign Ballard helps Lt. Torres in Engineering, she begins to speak Kobali, the rest of the crew, including B'Elanna, half Klingon, looks at her like they've never heard an alien language before.
During the 1 hour of recreation that Seven of Nine allotted for the children in the mess hall, Naomi Wildman says that Azan is cheating. While yes, this is true and Seven punished the children for cheating, Seven herself cheated on a puzzle earlier in season 5's Think Tank (1999). She shouldn't be punishing them for something she's guilty of doing herself.