When starting up the warp engine, Lt. Cmdr. Lynch sets the ratio for the matter-antimatter injectors at 25:1, yet, in Coming of Age (1988) it was established that there is only one ratio with matter-antimatter - 1:1.
When Worf first describes the half-buried shuttle, the top portion of the monitor display (above the topographical map with the shuttle) shows the full energy graph long before the discovery of the energy fluctuations; then, after the fluctuations are discovered, the graph is shown at its beginning.
(at around 29 mins) When Picard crouches down while talking to Armus, the top of Armus' "head" can be seen rising out of the pool, in the lower right corner of the shot facing Picard. Then, in the immediate next shot facing the pool, Armus breaks the surface and rises again.
After Armus attacks Yar, Crusher runs to her immediately while Riker and Data stand and fire their phasers at Armus before following her. Crusher has a good seven second head start on the others, but they all reach Yar at about the same time.
Just before the Enterprise is able to beam up Deanna, Ben, and Picard, Worf tells Wesley to have the computer beam them up when Armus's force field energy is less than 2.6.205. Decimal numbers are not read this way; only one decimal point is needed to separate the whole and fractional part of a number represented in decimal notation.
Geordi's phaser falls off into the oil slick-like creature (Armus) when he runs up to try and rescue Riker; however, it doesn't fall entirely into the pool but lands on its edge. Geordi, therefore, would have been able to pick it up and clean it, which is why he can later be seen with his phaser back in its holster.
At the end of Star Trek II: The Wrath of Khan (1982), Cmdr. Spock exposes himself to a fatal dose of radiation by manually realigning the dilithium crystals in the Enterprise's warp core, thus enabling the ship to escape destruction. However, at the start of this episode, Lt. Lynch not only safely realigns the Enterprise dilithium crystals by hand, he does so after casually walking the crystals through Engineering. Since this episode takes place about 80 years after the movie, it is possible some new safety measures were installed.
When Armus re-emerges from his pool for the first time, the slime can be seen bubbling right at the area where the mouth would be. (This is because the actor in the costume had to spit out the goo in order to breathe after coming to the surface.)
When Armus "removes" Geordi's visor forcefully to toy with him and Data, LeVar Burton's brown eyes are visible as the visor leaves his face (especially visible with freeze frame). The Geordi character is blind, with fully white eyeballs instead of colored irises.
As Armus pulls Commander Riker toward him, a wire can be seen disturbing the sand and the surface of the slime pool directly behind Riker.
In exterior shots of the crashed shuttle, there are no skid marks or drag marks in the dirt behind it, as one would expect in a crash of this nature in a calm environment.
The CG model of Armus is completely smooth, while the physical pool used to represent him has visible bubbles and ripples along its surface.
When Cmdr Riker is dragged into the Armus the away team rush to help. As they reach the edge of Armus, just as Riker disappears, Geordie's phaser drops into Armus.
As Captain Picard walks up to the pool of slime for the first time, two white lights reflect off the surface. The same is also true in shots of Armus covering the shuttle. This has to be a reflection of studio lights, since there is no other sign of life on the planet and no other white light on the planet.
Despite Yar's injuries, she is not beamed directly to Sickbay. No reason for this is given.
Data, as third in command, should relieve Worf as soon as he returns to the ship and enters the bridge, yet he does not.
When Worf first scans for the crashed shuttle, he says it is buried under a lot of debris. However, the first scene with the shuttle shows it in pieces next to a small hill, but it in no sense buried under anything.
Towards the end of the story Worf says the temperature is 2.6.3, he obviously means 2.63.