No series that has run as long as Star Trek has will be free of continuity errors. For proof of this, head over to WhoCulture and track some of the litany of errors that have followed that franchise through the years. However, to say that counting up some of these mistakes isn't fun would just be a downright lie.
Sometimes, a continuity error is just a small thing, barely noticeable. It might be the alignment of a hull or the design of a model. These things can easily be explained away in-universe, without doing too much damage to canon. On the flipside, there are sometimes a mistake is so glaring that it is a wonder it wasn't caught during the scripting process, long before it ever made it to filming. What's more, in some of the cases listed here, these events were spotted by the people behind the camera, and left in anyway to see if anyone noticed.
Stil, it's hard to be too harsh to Star Trek - it has given us so much enjoyment over the years. But there's still a job to be done here, so let's grab out raktajinos and dive right in.
10. Scotty Was On The Enterprise-B
With both Star Trek: Generations and Relics, the sixth-season episode of The Next Generation, featuring Scotty, there was bound to be a clash of continuity here. Both scripts were co-written by Ronald D. Moore, which makes the error here a little more egregious. In Relics, Scotty is saved from suspended animation in a transporter beam, believing Kirk to be his saviour.
However, in Star Trek: Generations, Scotty is on board the Enterprise-B as it encounters the Nexus. This mission was one for the history books, as even Riker is able to instantly identify it as the mission 'where James Kirk died.'
In the years that have passed, Scotty's apparent memory failure has been put down to signal degradation while trapped in the transporter, but the truth is far more simple. Generations hadn't been written by the time Relics was airing, and Scotty was a last-minute addition to the film when both Leonard Nimoy and Deforest Kelley either refused or were unable to appear.
This is more apparent in Generations than anything, as Scotty's dialogue is much more 'Spock-y' than ever, owing to the fact that the Vulcan's lines were handed more or less wholesale over to the engineer.