When Seven first sees one of the aliens, she enters the turbolift and asks for Deck 5. She exits the turbolift and enters the mess hall. The mess hall is on Deck 2 of the ship, not Deck 5.
At around 43:03, when Harry interrupts Tom and B'Elanna's dinner, the shot of B'Elanna with her chin on her hand is reversed: her hair is shown as down on the left side and pulled back on the right. In the rest of the scene, it it down on her right side and pulled back on the left.
When Janeway takes over the helm controls, Tuvok is standing behind her to her left, with Seven a little further back but on her right. A moment later, Seven is still in the same spot but Tuvok is suddenly back at his primary station several feet behind Seven.
The double helix for human DNA spirals in a specific orientation. The DNA in the Doctor's microscope is "left handed" spiraling in the wrong direction. Real DNA would be right handed. (If you grabbed the DNA with your index finger running along the backbone it would only work with your right hand.)
Paris orders the computer to conduct a site-to-site transport as a way to "sneak off" discreetly to meet Torres for a romantic encounter. In other episodes, however, Kim or someone else at the ops station on the bridge would have immediately reported to the captain an unauthorized attempt to access a transporter. Paris, being a deck officer, likely has the authority to circumvent the computer's ability to detect or report the transport this time.
When Neelix brings Chakotay some water he holds the glass steady very easily. However later he shows his "inability" to hold the glass steady when Neelix and him are comparing their disorders to each other.
In the opening scene, the Doctor provides Captain Janeway with a back massage. As he massages her, he mentions that she is "fortunate to have a masseur that can work all day without tiring." He says this while being extremely out of breath.
If the alien genetic tags are slightly out of phase and unable to be detected, then it stands to reason that they shouldn't be able to be seen by the Doctor and B'Elanna. Especially since the aliens are also out of phase on the same frequency. If the aliens can't be seen neither should the tags in the DNA.
As soon as he is "healed," Chakotay's hair grows back to its same length and gray distribution as it was prior to his illness.